Abadie, J., Abbott, B.P., Abbott, R., Adhikari, R., Ajith, P., Allen, B., Allen, G., Amador Ceron, E., Amin, R.S., Anderson, S.B., Anderson, W.G., Arain, M.A., Araya, M., Aso, Y., Aston, S., Aufmuth, P., Aulbert, C., Babak, S., Baker, P., Ballmer, S., Barker, D., Barr, B., Barriga, P., Barsotti, L., Barton, M.A., Bartos, I., Bassiri, R., Bastarrika, M., Behnke, B., Benacquista, M., Bennett, M.F., Betzwieser, J., Beyersdorf, P.T., Bilenko, I.A., Billingsley, G., Biswas, R., Black, E., Blackburn, J.K., Blackburn, L., Blair, D., Bland, B., Bock, O., Bodiya, T.P., Bondarescu, R., Bork, R., Born, M., Bose, S., Brady, P.R., Braginsky, V.B., Brau, J.E., Breyer, J., Bridges, D.O., Brinkmann, M., Britzger, M., Brooks, A.F., Brown, D.A., Bullington, A., Buonanno, A., Burmeister, O., Byer, R.L., Cadonati, L., Cain, J., Camp, J.B., Cannizzo, J., Cannon, K.C., Cao, J., Capano, C., Cardenas, L., Caudill, S., CavagliàM., Cepeda, C., Chalermsongsak, T., Chalkley, E., Charlton, P., Chatterji, S., Chelkowski, S., Chen, Y., Christensen, N., Chua, S.S.Y., Chung, C.T.Y., Clark, D., Clark, J., Clayton, J.H., Conte, R., Cook, D., Corbitt, T.R.C., Cornish, N., Coward, D., Coyne, D.C., Creighton, J.D.E., Creighton, T.D., Cruise, A.M., Culter, R.M., Cumming, A., Cunningham, L., Dahl, K., Danilishin, S.L., Danzmann, K., Daudert, B., Davies, G., et al., 2011, "Search for gravitational waves associated with the August 2006 timing glitch of the Vela pulsar," Physical Review D, 83, 42001.

 

       The physical mechanisms responsible for pulsar timing glitches are thought to excite quasinormal mode oscillations in their parent neutron star that couple to gravitational-wave emission. In August 2006, a timing glitch was observed in the radio emission of PSR B0833-45, the Vela pulsar. At the time of the glitch, the two colocated Hanford gravitational-wave detectors of the Laser Interferometer Gravitational-wave observatory (LIGO) were operational and taking data as part of the fifth LIGO science run (S5). We present the first direct search for the gravitational-wave emission associated with oscillations of the fundamental quadrupole mode excited by a pulsar timing glitch. No gravitational-wave detection candidate was found. We place Bayesian 90% confidence upper limits of 6.3×0^-21 to 1.4×0^-20 on the peak intrinsic strain amplitude of gravitational-wave ring-down signals, depending on which spherical harmonic mode is excited. The corresponding range of energy upper limits is 5.0×0⁴⁴ to 1.3×0⁴⁵ erg.

 

 

Adams, E.R., Ló-Morales, M., Elliot, J.L., Seager, S., Osip, D.J., 2011, "Transit Timing Variation Analysis of OGLE-TR-132b with Seven New Transits," The Astrophysical Journal, 728, 125.

 

       We report the results of the first transit timing variation analysis of the very hot Jupiter OGLE-TR-132b, using 10 transits collected over a seven-year period. Our analysis combines three previously published transit light curves with seven new transits, which were observed between 2008 February and 2009 May with the new MagIC-e2V instrument on the Magellan Telescopes in Chile. We provide a revised planetary radius of R_p = 1.23 ± 0.07R_J , which is slightly larger, but consistent within the errors, than that given by previously published results. Analysis of the planet-to-star radius ratio, orbital separation, inclination, and transit duration reveals no apparent variation in any of those parameters during the time span observed. We also find no sign of transit timing variations larger than .108 ± 49 s, with most residuals very close to zero. This allows us to place an upper limit of 5-10 M_E for a coplanar, low-eccentricity perturber in either the 2:1 or 3:2 mean-motion resonance with OGLE-TR-132b. We similarly find that the data are entirely consistent with a constant orbital period and there is no evidence for orbital decay within the limits of precision of our data.

 

 

Aubert, J., Dumberry, M., 2011, "Steady and fluctuating inner core rotation in numerical geodynamo models," Geophysical Journal International, 184, 162-170.

 

       We present a systematic survey of numerical geodynamo simulations where the inner core is allowed to differentially rotate in the longitudinal direction with respect to the mantle. We focus on the long-term behaviour of inner core rotation, on timescales much longer than the overturn time of the fluid outer core, including the steady component of rotation. The inner core is subject to viscous and magnetic torques exerted by the fluid outer core, and a gravitational restoring torque exerted by the mantle. We show that the rate of steady inner core rotation is limited by the differential rotation between spherical surfaces that the convective dynamics can sustain across the fluid outer core. We further show that this differential rotation is determined by a torque balance between the resistive Lorentz force and the Coriolis force on spherical surfaces within the fluid core. We derive a scaling law on the basis of this equilibrium suggesting that the ratio of the steady inner core rotation to typical angular velocity within the fluid core should be proportional to the square root of the Ekman number, in agreement with our numerical results. The addition of gravitational coupling does not alter this scaling, though it further reduces the amplitude of inner core rotation. In contrast, the long-term fluctuations in inner core rotation remain proportional to the fluid core angular velocity, with no apparent dependency on the Ekman number. If the same torque balance pertains to the Earth's core conditions, the inner core rotation then consists in a very slow super rotation of a few degrees per million years, superimposed over large fluctuations (at about a tenth of a degree per year). This suggests that the present-day seismically inferred inner core rotation is a fragment of a time-varying signal, rather than a steady super rotation. For the inner core rotation fluctuations not to cause excessive variations in the length-of-day, the strength of the gravitational coupling between the inner core and the mantle must be smaller than previously published values. We finally explore how the torque balance which we observe in our models could be altered in planetary cores, yielding possibly larger values of the steady rotation.

 

 

Audet, P., 2011, "Directional wavelet analysis on the sphere: Application to gravity and topography of the terrestrial planets," Journal of Geophysical Research (Planets), 116, 01003.

 

       The spectral relations (admittance and correlation) between gravity and topography are often used to obtain information on the density structure, flexural support, and heat flow of planetary lithospheres. Mapping spatial variations in these quantities requires spatiospectral analysis techniques. Here we describe the application of a directional, continuous spherical wavelet transform using a wavelet basis constructed from the superposition of azimuthally adjacent complex Morlet wavelets, in a manner similar to the .fan. wavelet developed in the plane. The method is applied to gravity and topography of the Earth, Venus, Mars, and the Moon. The wavelet coefficients are used to compute isotropic and directional wavelet autospectra and cross spectra, which are then combined to form the admittance and correlation functions. The resulting maps offer insights into lithospheric structure of the terrestrial planets. In particular we show that the Earth and Venus have uniformly low positive admittance and high correlation, whereas Mars and the Moon display hemispherical contrasts with large negative and anisotropic coefficients coinciding with lowlands. As has long been known, the two largest impact basins in the inner solar system, the South Pole.Aitken basin on the Moon and the Hellas basin on Mars, display low positive admittance and high correlation, indicating isostatic compensation. In contrast, most other impact basins, particularly the Martian and lunar mascons, show negative coefficients at low wavelet degrees suggesting flexural support by a strong lithosphere. These results imply that, although simple isotropic flexural models can account for most observations, future models may need to incorporate anisotropy as an additional parameter.

 

 

Barnes, R., Greenberg, R., Quinn, T.R., McArthur, B.E., Benedict, G.F., 2011, "Origin and Dynamics of the Mutually Inclined Orbits of n Andromedae c and d," The Astrophysical Journal, 726, 71.

 

       We evaluate the orbital evolution and several plausible origin scenarios for the mutually inclined orbits of n And c and d. These two planets have orbital elements that oscillate with large amplitudes and lie close to the stability boundary. This configuration, and in particular the observed mutual inclination, demands an explanation. The planetary system may be influenced by a nearby low-mass star, n And B, which could perturb the planetary orbits, but we find it cannot modify two coplanar orbits into the observed mutual inclination of 30°. However, it could incite ejections or collisions between planetary companions that subsequently raise the mutual inclination to >30°. Our simulated systems with large mutual inclinations tend to be further from the stability boundary than n And, but we are able to produce similar systems. We conclude that scattering is a plausible mechanism to explain the observed orbits of n And c and d, but we cannot determine whether the scattering was caused by instabilities among the planets themselves or by perturbations from n And B. We also develop a procedure to quantitatively compare numerous properties of the observed system to our numerical models. Although we only implement this procedure to n And, it may be applied to any exoplanetary system.

 

 

Beuermann, K., Buhlmann, J., Diese, J., Dreizler, S., Hessman, F.V., Husser, T.-O., Miller, G.F., Nickol, N., Pons, R., Ruhr, D., Schmü, H., Schwope, A.D., Sorge, T., Ulrichs, L., Winget, D.E., Winget, K.I., 2011, "The giant planet orbiting the cataclysmic binary DP Leonis," Astronomy and Astrophysics, 526, 53.

 

       Planets orbiting post-common envelope binaries provide fundamental information on planet formation and evolution, especially for the yet nearly unexplored class of circumbinary planets. We searched for such planets in DP Leo, an eclipsing short-period binary, which shows long-term eclipse-time variations. Using published, reanalysed, and new mid-eclipse times of the white dwarf in DP Leo, obtained between 1979 and 2010, we find agreement with the light-travel-time effect produced by a third body in an elliptical orbit. In particular, the measured binary period in 2009/2010 and the implied radial velocity coincide with the values predicted for the motion of the binary and the third body around the common center of mass. The orbital period, semi-major axis, and eccentricity of the third body are P_c = 28.0 ± 2.0 yrs, a_c = 8.2 ± 0.4 AU, and e_c = 0.39 ± 0.13. Its mass of sin i_c M_c = 6.1 ± 0.5 M_Jup qualifies it as a giant planet. It formed either as a first generation object in a protoplanetary disk around the original binary or as a second generation object in a disk formed in the common envelope shed by the progenitor of the white dwarf. Even a third generation origin in matter lost from the present accreting binary can not be entirely excluded. We searched for, but found no evidence for a fourth body.

 

 

Billings, L., 2011, "Astronomy: Exoplanets on the cheap," Nature, 470, 27-29.

 

       The search for planets outside our Solar System will always be pricey. But creative solutions are proving that it no longer has to break the bank.

 

 

Bizouard, C., Remus, F., Lambert, S.B., Seoane, L., Gambis, D., 2011, "The Earth's variable Chandler wobble," Astronomy and Astrophysics, 526, 106.

 

       Aims: We investigated the causes of the Earth's Chandler wobble variability over the past 60 years. Our approach is based on integrating of the atmospheric and oceanic angular momentum computed by global circulation models. We directly compared the result of the integration with the Earth's pole coordinate observed by precise astrometric, space, and geodetic techniques. This approach differs from the traditional approach in which the observed polar motion is transformed into a so-called geodetic excitation function, and compared afterwards with the angular momentum of the external geophysical fluid layers.

 

Methods: In the time domain, we integrated the atmospheric angular momentum time series from the National Center for Environmental Prediction/National Center for Atmospheric Research Reanalysis project and the oceanic angular momentum data from the ECCO consortium. We extracted the Chandler wobble from this modeled polar motion by singular spectrum analysis, and compared it with the Chandler wobble extracted from the observed polar motion given by the International Earth Rotation and Reference Systems Service data.

 

Results: We showed that the combination of the atmosphere and the oceans explains most of the observed Chandler wobble variations, and is consistent with results reported in the literature and obtained with the traditional approach. Our approach allows one to appreciate the separate contributions of the atmosphere and the oceans to the various bumps and valleys observed in the Chandler wobble. Though the atmosphere explains the Chandler wobble amplitude variations between 1949 and 1970, the reexcitation of the Chandler wobble that begins in the 1980s, after a minimum around 1970, and that reaches its maximum in the late 1990s is due to the oceans, while the atmospheric contribution remains stable within the same period.

 

 

Blanchet, L., Novak, J., 2011, "External field effect of modified Newtonian dynamics in the Solar system," Monthly Notices of the Royal Astronomical Society, 76.

 

       The modified Newtonian dynamics (MOND) have been formulated as a modification of the Poisson equation for the Newtonian gravitational field. This theory generically predicts a violation of the strong version of the equivalence principle and as a result, the gravitational dynamics of a system depend on the external gravitational field in which the system is embedded. This so-called external field effect has been recently shown to imply the existence of an anomalous quadrupolar correction, along the direction of the external galactic field, in the gravitational potential felt by planets in the Solar system. In this paper, we confirm the existence of this effect by a numerical integration of the MOND equation in the presence of an external field and compute the secular precession of the perihelion of planets induced by this effect. We find that the precession effect is rather large for outer gaseous planets and in the case of Saturn, it is comparable to published residuals of precession obtained by Saturn range tracking data. The effect is much smaller for inner planets, but in the case of the Earth, it appears to be in conflict for most of the MOND functions m(y) with the very good constraint on the perihelion precession obtained from Jupiter very long baseline interferometry data. The MOND functions that are compatible with this constraint appear to have a very rapid transition from the MONDian regime to the Newtonian one.

 

 

 

 

Book, L.G., Flanagan, ÉÉ, 2011, "Astrometric effects of a stochastic gravitational wave background," Physical Review D, 83, 24024.

 

       A stochastic gravitational wave background causes the apparent positions of distant sources to fluctuate, with angular deflections of order the characteristic strain amplitude of the gravitational waves. These fluctuations may be detectable with high precision astrometry, as first suggested by Braginsky et al. in 1990. Several researchers have made order of magnitude estimates of the upper limits obtainable on the gravitational wave spectrum W_gw(f), at frequencies of order ~ 1yr^-1, both for the future space-based optical interferometry missions GAIA and SIM, and for very long baseline interferometry in radio wavelengths with the SKA. For GAIA, tracking N~10⁶ quasars over a time of ~1yr with an angular accuracy of Dq~10m as would yield a sensitivity level of W_gw ~ (Dq)²/(NT²H₀²)~10^-6, which would be comparable with pulsar timing. In this paper we take a first step toward firming up these estimates by computing in detail the statistical properties of the angular deflections caused by a stochastic background. We compute analytically the two-point correlation function of the deflections on the sphere, and the spectrum as a function of frequency and angular scale. The fluctuations are concentrated at low frequencies (for a scale invariant stochastic background), and at large angular scales, starting with the quadrupole. The magnetic-type and electric-type pieces of the fluctuations have equal amounts of power.

 

 

Borucki, W.J., Koch, D.G., Basri, G., Batalha, N., Boss, A., Brown, T.M., Caldwell, D., Christensen-Dalsgaard, J., Cochran, W.D., DeVore, E., Dunham, E.W., Dupree, A.K., Gautier, T.N., III, Geary, J.C., Gilliland, R., Gould, A., Howell, S.B., Jenkins, J.M., Kjeldsen, H., Latham, D.W., Lissauer, J.J., Marcy, G.W., Monet, D.G., Sasselov, D., Tarter, J., Charbonneau, D., Doyle, L., Ford, E.B., Fortney, J., Holman, M.J., Seager, S., Steffen, J.H., Welsh, W.F., Allen, C., Bryson, S.T., Buchhave, L., Chandrasekaran, H., Christiansen, J.L., Ciardi, D., Clarke, B.D., Dotson, J.L., Endl, M., Fischer, D., Fressin, F., Haas, M., Horch, E., Howard, A., Isaacson, H., Kolodziejczak, J., Li, J., MacQueen, P., Meibom, S., Prsa, A., Quintana, E.V., Rowe, J., Sherry, W., Tenenbaum, P., Torres, G., Twicken, J.D., Van Cleve, J., Walkowicz, L., Wu, H., 2011, "Characteristics of Kepler Planetary Candidates Based on the First Data Set," The Astrophysical Journal, 728, 117.

 

       In the spring of 2009, the Kepler Mission commenced high-precision photometry on nearly 156,000 stars to determine the frequency and characteristics of small exoplanets, conduct a guest observer program, and obtain asteroseismic data on a wide variety of stars. On 2010 June 15, the Kepler Mission released most of the data from the first quarter of observations. At the time of this data release, 705 stars from this first data set have exoplanet candidates with sizes from as small as that of Earth to larger than that of Jupiter. Here we give the identity and characteristics of 305 released stars with planetary candidates. Data for the remaining 400 stars with planetary candidates will be released in 2011 February. More than half the candidates on the released list have radii less than half that of Jupiter. Five candidates are present in and near the habitable zone; two near super-Earth size, and three bracketing the size of Jupiter. The released stars also include five possible multi-planet systems. One of these has two Neptune-size (2.3 and 2.5 Earth radius) candidates with near-resonant periods.

 

 

Bouchy, F., Deleuil, M., Guillot, T., Aigrain, S., Carone, L., Cochran, W.D., Almenara, J.M., Alonso, R., Auvergne, M., Baglin, A., Barge, P., Bonomo, A.S., BordéP., Csizmadia, S., de Bondt, K., Deeg, H.J., Dí, R.F., Dvorak, R., Endl, M., Erikson, A., Ferraz-Mello, S., Fridlund, M., Gandolfi, D., Gazzano, J.C., Gibson, N., Gillon, M., Guenther, E., Hatzes, A., Havel, M., Héard, G., Jorda, L., Lér, A., Lovis, C., Llebaria, A., Lammer, H., MacQueen, P.J., Mazeh, T., Moutou, C., Ofir, A., Ollivier, M., Parviainen, H., Päold, M., Queloz, D., Rauer, H., Rouan, D., Santerne, A., Schneider, J., Tingley, B., Wuchterl, G., 2011, "Transiting exoplanets from the CoRoT space mission. XV. CoRoT-15b: a brown-dwarf transiting companion," Astronomy and Astrophysics, 525, 68.

 

       We report the discovery by the CoRoT space mission of a transiting brown dwarf orbiting a F7V star with an orbital period of 3.06 days. CoRoT-15b has a radius of 1.12^+0.30_-0.15R_Jup and a mass of 63.3 ± 4.1 M_Jup, and is thus the second transiting companion lying in the theoretical mass domain of brown dwarfs. CoRoT-15b is either very young or inflated compared to standard evolution models, a situation similar to that of M-dwarf stars orbiting close to solar-type stars. Spectroscopic constraints and an analysis of the lightcurve imply a spin period in the range 2.9-3.1 days for the central star, which is compatible with a double-synchronisation of the system.

 

 

Bourda, G., Collioud, A., Charlot, P., Porcas, R., Garrington, S., 2011, "VLBI observations of optically-bright extragalactic radio sources for the alignment of the radio frame with the future Gaia frame. II. Imaging candidate sources," Astronomy and Astrophysics, 526, 102.

 

       Context. The European space astrometry mission Gaia, to be launched by 2012, will construct a dense optical QSO-based celestial reference frame which will need to be linked to the International Celestial Reference Frame (ICRF; the IAU fundamental frame), with the highest accuracy. However, it has been found that only 10% of the ICRF sources (70 sources) are suitable to establish this link. The remaining sources are not useful either because they are not bright enough at optical wavelengths or because they have significant extended radio emission which precludes reaching the highest astrometric accuracy

 

Aims: In order to improve the accuracy of this alignment, we have developed a program of VLBI observations based on three steps to detect, image and measure astrometric positions of weak extragalactic radio sources, with bright optical counterparts, from a sample of 447 candidate sources.

 

Methods: The experiments devoted to VLBI detection, carried out with the European VLBI Network (EVN) in June and October 2007, were very successful, with 398 sources detected at both S- and X-bands. From these, 105 sources were observed in March 2008 with a global VLBI array (EVN and VLBA; Very Long Baseline Array) for imaging their VLBI structures.

 

Results: All sources were successfully imaged in both bands and about 50% (47 sources) were found to be point-like on VLBI scales. These images are available at http://www.obs.u-bordeaux1.fr/BVID/GC030/. VLBI positions of these sources will be measured accurately in future astrometric experiments. Full Table 3 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/viz-bin/qcat?J/A+A/526/A102

 

 

Breiter, S., Vokrouhlický 2011, "Yarkovsky-O'Keefe-Radzievskii-Paddack effect with anisotropic radiation," Monthly Notices of the Royal Astronomical Society, 410, 2807-2816.

 

       In this paper, we study the influence of optical scattering and thermal radiation models on the Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect. The Lambertian formulation is compared with the scattering and emission laws and Lommel-Seeliger reflection. Although the form of the reflectivity function strongly influences the mean torques because of scattering or thermal radiation alone, their combined contribution to the rotation period YORP effect is not very different from the standard Lambertian values. For higher albedo values, the differences between the Hapke and Lambert models become significant for the YORP effect in attitude.

 

 

Budaj, J., 2011, "The Reflection Effect in Interacting Binaries or in Planet-Star Systems," The Astronomical Journal, 141, 59.

 

       There are many similarities between interacting binary stars and stars with a close-in giant extrasolar planet. The reflection effect is a well-known example. Although the generally accepted treatment of this effect in interacting binaries is successful in fitting light curves of eclipsing binaries, it is not very suitable for studying cold objects irradiated by hot objects or extrasolar planets. The aim of this paper is to develop a model of the reflection effect which could be easily incorporated into the present codes for modeling of interacting binaries so that these can be used to study the aforementioned objects. Our model of the reflection effect takes into account the reflection (scattering), heating, and heat redistribution over the surface of the irradiated object. The shape of the object is described by the non-spherical Roche potential expected for close objects. Limb and gravity darkening are included in the calculations of the light output from the system. The model also accounts for the orbital revolution and rotation of the exoplanet with appropriate Doppler shifts for the scattered and thermal radiation. Subsequently, light curves and/or spectra of several exoplanets have been modeled and the effects of the heat redistribution, limb darkening/brightening, (non-)gray albedo, and non-spherical shape have been studied. Recent observations of planet-to-star flux ratio of HD189733b, WASP12b, and WASP-19b at various phases were reproduced with very good accuracy. It was found that HD189733b has a low Bond albedo and intense heat redistribution, while WASP-19b has a low Bond albedo and low heat redistribution. The exact Roche geometries and temperature distributions over the surface of all 78 transiting extrasolar planets have been determined. Departures from the spherical shape may vary considerably but departures of about 1% in the radius are common within the sample. In some cases, these departures can reach 8%, 12%, or 14%, for WASP-33b, WASP-19b, and WASP-12b, respectively. The mean temperatures of these planets also vary considerably from 300 K to 2600 K. The extreme cases are WASP-18b, WASP-12b, and WASP-33b, with mean temperatures of 2330 K, 2430 K, and 2600 K, respectively.

 

 

Campo, C.J., Harrington, J., Hardy, R.A., Stevenson, K.B., Nymeyer, S., Ragozzine, D., Lust, N.B., Anderson, D.R., Collier-Cameron, A., Blecic, J., Britt, C.B.T., Bowman, W.C., Wheatley, P.J., Loredo, T.J., Deming, D., Hebb, L., Hellier, C., Maxted, P.F.L., Pollaco, D., West, R.G., 2011, "On the Orbit of Exoplanet WASP-12b," The Astrophysical Journal, 727, 125.

 

       We observed two secondary eclipses of the exoplanet WASP-12b using the Infrared Array Camera on the Spitzer Space Telescope. The close proximity of WASP-12b to its G-type star results in extreme tidal forces capable of inducing apsidal precession with a period as short as a few decades. This precession would be measurable if the orbit had a significant eccentricity, leading to an estimate of the tidal Love number and an assessment of the degree of central concentration in the planetary interior. An initial ground-based secondary-eclipse phase reported by Ló-Morales et al. (0.510 ± 0.002) implied eccentricity at the 4.5s level. The spectroscopic orbit of Hebb et al. has eccentricity 0.049 ± 0.015, a 3 s result, implying an eclipse phase of 0.509 ± 0.007. However, there is a well-documented tendency of spectroscopic data to overestimate small eccentricities. Our eclipse phases are 0.5010 ± 0.0006 (3.6 and 5.8 mm) and 0.5006 ± 0.0007 (4.5 and 8.0 mm). An unlikely orbital precession scenario invoking an alignment of the orbit during the Spitzer observations could have explained this apparent discrepancy, but the final eclipse phase of Ló-Morales et al. (0.510 ±^+0.007_.0.006) is consistent with a circular orbit at better than 2s. An orbit fit to all the available transit, eclipse, and radial-velocity data indicates precession at <1s a non-precessing solution fits better. We also comment on analysis and reporting for Spitzer exoplanet data in light of recent re-analyses.

 

 

 

Carruba, V., Machuca, J.F., Gasparino, H.P., 2011, "Dynamical erosion of asteroid groups in the region of the Pallas family," Monthly Notices of the Royal Astronomical Society, 93.

 

       In a previous paper, the current state of knowledge on the region of the Pallas dynamical family was revised. Here the dynamical evolution and possible origin of dynamical groups in the region are investigated. First, we study the case of asteroids at high eccentricity (e > 0.31). These objects are unstable because of encounters with Mars on time-scales of up to 340 Myr. Local background asteroids are currently the major source of high-eccentricity objects, but Barcelona family members will become the dominant source in about 250 Myr. Next, attention is focused on the lack of chaotic dynamics near the n₆ secular resonance border in the region. Contrary to the case of the Phocaea family region, very limited chaotic behaviour was observed for real and fictitious particles in the central main belt near the n₆ resonance. Using analytical and numerical tools, we find that the limited amplitude of the inclination region near the n₆ resonance in the Pallas family region for which close encounters with Mars are possible explains the lack of chaotic behaviour found in a previous paper by Carruba. Finally, we investigate the long-term stability of the minor families and clumps identified in the previous paper, when non-gravitational effects are considered. We find that none of the minor clumps obtained by Carruba is currently interacting with non-linear secular resonances in the region. The classical clumps around (40134) 1998 QO53, (75938) 2000 CO80, (33969) 2000 NM13, (208080) 1999 VV180 and (70280) 1999 RA111 have large detectability times and could be considered reasonable candidates for groups originating from collisional events. We confirm the presence of the (4203) Brucato family observable in the space of proper frequencies (n, g, g+s) that has the largest detectability time of all groups in the region.

 

 

Carruba, V., Morbidelli, A., 2011, "On the first n₆ anti-aligned librating asteroid family of Tina," Monthly Notices of the Royal Astronomical Society, 96.

 

       Asteroid families are groups of bodies identified in the space of proper elements or of frequencies that share a common origin in the collisional break-up of their progenitors. Their dynamical evolution is shaped by the interaction with the local web of mean-motion and secular resonances, and by non-gravitational effects, such as the 'Yarkovsky' and 'Yarkovsky-O'Keefe-Radzievskii-Paddack' (YORP) effects. Thus, obtaining information on their age and original ejection velocity field is generally a difficult task. Recently, two families were found to have a large fraction of members in the non-linear secular resonance z₁: the Agnia and Padua families. Conserved quantities of the z₁resonance allowed for a more precise determination of their ages and ejection velocity fields. So far, however, no family was known to be in a linear secular resonance, such as the n₆ resonance, although individual asteroids were known to be in n₆ anti-aligned librating states. The n₆ resonance occurs when there is a commensurability between the frequency of precession of the pericentre of an asteroid and that of Saturn. As a consequence, in librating states, the resonant argument oscillates around a stable point. In anti-aligned librating states, the resonant argument oscillates around the stable point at 180°. Here we show that the newly identified Tina family is characterized by having all its members in such a state, making it the only family in the asteroid belt known to be completely embedded in a secular resonance configuration. This rare dynamical configuration limits the maximum eccentricity of Tina members, preventing them from experiencing Martian close encounters and forming a stable island of a new dynamical type. The current dispersion of asteroid resonant elements suggests that the family should be at least 2.5 Myr old, while Monte Carlo simulations including the Yarkovsky and YORP effects suggest that the Tina family should be 170⁺²⁰_-30 Myr old.

 

 

Carter, J.A., Rappaport, S., Fabrycky, D., 2011, "A Third Hot White Dwarf Companion Detected by Kepler," The Astrophysical Journal, 728, 139.

 

       We have found a system listed in the Kepler Binary Catalog (P _orb = 3.273 days) that we have determined is comprised of a low-mass, thermally bloated, hot white dwarf orbiting an A star of about 2.3 M_sun. In this work, we designate the object, KIC 10657664, simply as "KHWD3" (Kepler Hot White Dwarf 3). We use the transit depth of ~0.66%, the eclipse depth of ~1.9%, and regular smooth periodic variations at the orbital frequency and twice the orbital frequency to analyze the system parameters. The smooth periodic variations are identified with the classical ellipsoidal light variation (ELV) and illumination (ILL) effects, and the newly utilized Doppler boosting (DB) effect. Given the measured values of R/a and inclination angle of the binary, both the ELV and DB effects are mostly sensitive to the mass ratio, q = M₂/M₁, of the binary. The two effects yield values of q which are somewhat inconsistent.presumably due to unidentified systematic effects.but which nonetheless provide a quite useful set of possibilities for the mass of the white dwarf (either 0.26 ± 0.04 M_sun or 0.37 ± 0.08 M_sun). All of the other system parameters are determined fairly robustly. In particular, we show that the white dwarf has a radius of 0.15 ± 0.01 R_sun, which is extremely bloated over the radius it would have as a fully degenerate object, and an effective temperature T_eff ~=14,500 K. Binary evolution scenarios and models for this system are discussed. We suggest that the progenitor binary was comprised of a primary of mass ~2.2 M_sun (the progenitor of the current hot white dwarf) and a secondary of mass ~1.4 M_sun (the progenitor of the current A star in the system). We compare this new system with three other white dwarfs in binaries that likely were formed via stable Roche-lobe overflow (KOI-74, KOI-81, and the inner Regulus binary).

 

 

 

Chang, H.-K., Liu, C.-Y., Chen, K.-T., 2011, "Millisecond dips in the 2007-09 RXTE/PCA light curve of Sco X-1 and one possible occultation event," Monthly Notices of the Royal Astronomical Society, 411, 427-434.

 

       Serendipitous stellar occultation search is so far the only way to detect the existence of very small, very dim, remote objects in the Solar system. To date, however, there are only very few reported detections for trans-Neptunian objects (TNOs) in optical bands. In the X-ray band, with the RXTE/PCA data of Sco X-1 taken from 2007 June to 2009 October, we found one possible X-ray occultation event. We discuss the veracity and properties of this event, and suggest upper limits to the size distribution of TNOs at hectometre size and of main-belt asteroids at decametre size.

 

 

Christiansen, J.L., Ballard, S., D., Deming, D., Holman, M.J., Madhusudhan, N., Seager, S., Wellnitz, D.D., Barry, R.K., Livengood, T.A., Hewagama, T., Hampton, D.L., Lisse, C.M., A'Hearn, M.F., 2011, "System Parameters, Transit Times, and Secondary Eclipse Constraints of the Exoplanet Systems HAT-P-4, TrES-2, TrES-3, and WASP-3 from the NASA EPOXI Mission of Opportunity," The Astrophysical Journal, 726, 94.

 

       As part of the NASA EPOXI Mission of Opportunity, we observed seven known transiting extrasolar planet systems in order to construct time series photometry of extremely high phase coverage and precision. Here we present the results for four "hot-Jupiter systems" with near-solar stars.HAT-P-4, TrES-3, TrES-2, and WASP-3. We observe 10 transits of HAT-P-4, estimating the planet radius R_p = 1.332 ± 0.052 R_Jup, the stellar radius R« = 1.602 ± 0.061 R_sun, the inclination i = 89.67 ± 0.30 deg, and the transit duration from first to fourth contact t = 255.6 ± 1.9 minutes. For TrES-3, we observe seven transits and find R_p = 1.320 ± 0.057 R_Jup, R« = 0.817 ± 0.022 R_sun, i = 81.99 ± 0.30 deg, and t = 81.9 ± 1.1 minutes. We also note a long-term variability in the TrES-3 light curve, which may be due to star spots. We observe nine transits of TrES-2 and find R_p = 1.169 ± 0.034 R_Jup, R« = 0.940 ± 0.026 R_sun, i = 84.15 ± 0.16 deg, and t = 107.3 ± 1.1 minutes. Finally, we observe eight transits of WASP-3, finding R_p = 1.385 ± 0.060 R_Jup, R« = 1.354 ± 0.056 R_sun, i = 84.22 ± 0.81 deg, and t = 167.3 ± 1.3 minutes. We present refined orbital periods and times of transit for each target. We state 95% confidence upper limits on the secondary eclipse depths in our broadband visible bandpass centered on 650 nm. These limits are 0.073% for HAT-P-4, 0.062% for TrES-3, 0.16% for TrES-2, and 0.11% for WASP-3. We combine the TrES-3 secondary eclipse information with the existing published data and confirm that the atmosphere likely does not have a temperature inversion.

 

 

Chung, S.-J., Lee, C.-U., 2011, "Properties of the planetary caustic perturbation," Monthly Notices of the Royal Astronomical Society, 411, 151-154.

 

       Just two of 10 extrasolar planets found by microlensing have been detected by the planetary caustic, despite the higher probability of planet detection relative to the central caustic, which has been responsible for four extrasolar planet detections. This is because the perturbations induced by the planetary caustic are unpredictable, thus making it difficult to carry out strategic observations. However, if future high-cadence monitoring surveys are conducted, the majority of planetary caustic events including the events by free-floating planets and wide-separation planets would be detected. Hence, understanding the planetary caustic perturbations becomes important. In this paper, we investigate in detail the pattern of the planetary caustic perturbations. From this study, we find three properties of the planetary caustic perturbations. First, planetary systems with the same star-planet separation (s) basically produce perturbations of constant strength, regardless of the planet-to-star mass ratio (q), but the duration of each perturbation scales with√q . Secondly, close planetary systems with the same separation produce essentially the same negative perturbations between two triangular-shaped caustics, regardless of q, but the duration of the perturbations scales with √q. Thirdly, the positive perturbations for planetary systems with the same mass ratio become stronger as the caustic shrinks with the increasing |log s|, while the negative perturbations become weaker. We estimate the degeneracy in the determination of q that occurs in planetary caustic events. From this, we find that the mass ratio can be more precisely determined as q increases and |log s| decreases. We also find that the degeneracy range of events for which the source star passes close to the planetary caustic is usually very narrow, and thus it would not significantly affect the determination of q.

 

 

Conidis, G.J., Sadavoy, S.I., Maxwell, A.J., Delaney, P.A., Manzer, L.H., 2011, "Period Changes in SX Phoenicis Stars. III. XX Cygni," Publications of the Astronomical Society of the Pacific, 123, 26-33.

 

       XX Cyg is a high-amplitude d Scuti star which has been extensively studied because of its changing period. We present 64 new times of maxima that have been combined with 174 times of maxima from literature, in order to give an updated ephemeris and O - C plot for XX Cyg. Its period, currently found to be 0.134865117(3) days, is shown to be increasing continuously, which has lead to a new calculated value of (1/P) (dP/dt) = 1.33 ( 7 ) · 10^-8 yr^-1.

 

 

Cowan, N.B., Agol, E., 2011, "A Model for Thermal Phase Variations of Circular and Eccentric Exoplanets," The Astrophysical Journal, 726, 82.

 

       We present a semi-analytic model atmosphere for close-in exoplanets that captures the essential physics of phase curves: orbital and viewing geometry, advection, and re-radiation. We calibrate the model with the well-characterized transiting planet, HD 189733b, then compute light curves for seven of the most eccentric transiting planets: Gl 436b, HAT-P-2b, HAT-P-11b, HD 17156b, HD 80606b, WASP-17b, and XO-3b. We present phase variations for a variety of different radiative times and wind speeds. In the limit of instant re-radiation, the light-curve morphology is entirely dictated by the planet's eccentricity and argument of pericenter: the light curve maximum leads or trails the eclipse depending on whether the planet is receding from or approaching the star at superior conjunction, respectively. For a planet with non-zero radiative timescales, the phase peak occurs early for super-rotating winds, and late for sub-rotating winds. We find that for a circular orbit, the timing of the phase variation maximum with respect to superior conjunction indicates the direction of the dominant winds, but cannot break the degeneracy between wind speed and radiative time. For circular planets the phase minimum occurs half an orbit away from the phase maximum.despite the fact that the coolest longitudes are always near the dawn terminator.and therefore does not convey any additional information. In general, increasing the advective frequency or the radiative time has the effect of reducing the peak-to-trough amplitude of phase variations, but there are interesting exceptions to these trends. Lastly, eccentric planets with orbital periods significantly longer than their radiative time exhibit "ringing," whereby the hot spot generated at periastron rotates in and out of view. The existence of ringing makes it possible to directly measure the wind speed (the frequency of the ringing) and the radiative time constant (the damping of the ringing).

 

 

Croll, B., Lafreniere, D., Albert, L., Jayawardhana, R., Fortney, J.J., Murray, N., 2011, "Near-infrared Thermal Emission from WASP-12b: Detections of the Secondary Eclipse in Ks, H, and J," The Astronomical Journal, 141, 30.

 

       We present Ks, H, & J-band photometry of the very highly irradiated hot Jupiter WASP-12b using the Wide-field Infrared Camera on the Canada-France-Hawaii telescope. Our photometry brackets the secondary eclipse of WASP-12b in the Ks and H bands, and in J band starts in mid-eclipse and continues until well after the end of the eclipse. We detect its thermal emission in all three near-infrared bands. Our secondary eclipse depths are 0.309^+0.013_.0.012% in Ks band (24s), 0.176^+0.016_.0.021% in H band (9s), and 0.131^+0.027_.0.029% in J band (4s). All three secondary eclipses are best fit with a consistent phase, phi, that is compatible with a circular orbit: phi = 0.4998^+0.0008_.0.0007. The limits on the eccentricity, e, and argument of periastron, w, of this planet from our photometry alone are thus |ecos w| < 0.0040. By combining our secondary eclipse times with others published in the literature, as well as the radial-velocity and transit-timing data for this system, we show that there is no evidence that WASP-12b is precessing at a detectable rate and that its orbital eccentricity is likely zero. Our thermal-emission measurements also allow us to constrain the characteristics of the planet's atmosphere; our Ks-band eclipse depth argues strongly in favor of inefficient day to nightside redistribution of heat and a low Bond albedo for this very highly irradiated hot Jupiter. The J- and H-band brightness temperatures are slightly cooler than the Ks-band brightness temperature, and thus hint at the possibility of a modest temperature inversion deep in the atmosphere of WASP-12b; the high-pressure, deep atmospheric layers probed by our J- and H-band observations are likely more homogenized than the higher altitude layer probed by our Ks-band observations. Lastly, our best-fit Ks-band eclipse has a marginally longer duration than would otherwise be expected; this may be tentative evidence for material being tidally stripped from the planet.as was predicted for this system by Li and collaborators, and for which observational confirmation was recently arguably provided by Fossati and collaborators.

 

 

Curiel, S., Cantó., Georgiev, L., Cház, C.E., Poveda, A., 2011, "A fourth planet orbiting n Andromedae," Astronomy and Astrophysics, 525, 78.

 

       We present a 4-planet Keplerian fit for the radial velocity curve of the F8V star ? Andromeda, indicating the presence of a fourth planet in the system. We detect an additional fifth coherent signal in the radial velocity curve which we attribute to stellar activity. The discovery of a new planet around n Andromedae makes this system the fifth to contain, at least, four planets. These four planets have minimum masses of 0.69, 1.98, 4.13 and 1.06 M_Jup and orbital periods of 4.62, 241.26, 1276.46 and 3848.9 days, respectively. We have numerically integrated the orbital solution for these four planets and find that the system is stable for at least 10 Myr. The orbit of the fourth planet coincides with an island of stability reported by Rivera & Haghighipour (2007, MNRAS, 374, 599). We find that the characteristics of the new fourth planet are very similar to those of Jupiter and that the planets in this system have very strong interactions with each other. As previously found, n And-b and n And-c are in apsidal alignment, while the orbit of the new planet (n And-e) is close to an external 3:1 resonance with n And-c.

 

 

de Marco, O., Passy, J.-C., Moe, M., Herwig, F., Mac Low, M.-M., Paxton, B., 2011, "On the a formalism for the common envelope interaction," Monthly Notices of the Royal Astronomical Society, 28.

 

       The a formalism is a common way to parametrize the common envelope interaction between a giant star and a more compact companion. The a parameter describes the fraction of orbital energy released by the companion that is available to eject the giant star.s envelope. By using new, detailed stellar evolutionary calculations, we derive a user-friendly prescription for the l parameter and an improved approximation for the envelope binding energy, thus revising the a equation. We then determine a both from simulations and from observations in a self-consistent manner. By using our own stellar structure models as well as population considerations to reconstruct the primary.s parameters at the time of the common envelope interaction, we gain a deeper understanding of the uncertainties. We find that systems with very low values of q (the ratio of the companion.s mass to the mass of the primary at the time of the common envelope interaction) have higher values of a. A fit to the data suggests that lower-mass companions are left at comparable or larger orbital separations to more massive companions. We conjecture that lower-mass companions take longer than a stellar dynamical time to spiral into the giant.s core, and that this is key to allowing the giant to use its own thermal energy to help unbind its envelope. As a result, although systems with light companions might not have enough orbital energy to unbind the common envelope, they might stimulate a stellar reaction that results in the common envelope ejection.

 

 

Delgado Mena, E., Israelian, G., Gonzáz Hernáez, J.I., Santos, N.C., Rebolo, R., 2011, "Measuring Be Depletion in Cool Stars with Exoplanets," The Astrophysical Journal, 728, 148.

 

       We present new UVES spectra of a sample of 14 mostly cool unevolved stars with planetary companions with the aim of studying possible differences in Be abundance with respect to stars without detected planets. We determine Be abundances for these stars that show an increase in Be depletion as we move to lower temperatures. We carry out a differential analysis of spectra of analog stars with and without planets to establish a possible difference in Be content. While for hot stars no measurable difference is found in Be, for the only cool (T_eff~ 5000 K) planet-host star with several analogs in the sample we find enhanced Be depletion by 0.25 dex. This is a first indication that the extra-depletion of Li in solar-type stars with planets may also happen for Be, but shifted toward lower temperatures (T_eff < 5500 K) due to the depth of the convective envelopes. The processes that take place in the formation of planetary systems may affect the mixing of material inside their host stars and hence the abundances of light elements

 

 

Deming, D., Knutson, H., Agol, E., Desert, J.-M., Burrows, A., Fortney, J.J., Charbonneau, D., Cowan, N.B., Laughlin, G., Langton, J., Showman, A.P., Lewis, N.K., 2011, "Warm Spitzer Photometry of the Transiting Exoplanets CoRoT-1 and CoRoT-2 at Secondary Eclipse," The Astrophysical Journal, 726, 95.

 

       We measure secondary eclipses of the hot giant exoplanets CoRoT-1 at 3.6 and 4.5 mm, and CoRoT-2 at 3.6 mm, both using Warm Spitzer. We find that the Warm Spitzer mission is working very well for exoplanet science. For consistency of our analysis we also re-analyze archival cryogenic Spitzer data for secondary eclipses of CoRoT-2 at 4.5 and 8 mm. We compare the total data for both planets, including optical eclipse measurements by the CoRoT mission, and ground-based eclipse measurements at 2 mm, to existing models. Both planets exhibit stronger eclipses at 4.5 than at 3.6 mm, which is often indicative of an atmospheric temperature inversion. The spectrum of CoRoT-1 is best reproduced by a 2460 K blackbody, due either to a high altitude layer that strongly absorbs stellar irradiance, or an isothermal region in the planetary atmosphere. The spectrum of CoRoT-2 is unusual because the 8 ?m contrast is anomalously low. Non-inverted atmospheres could potentially produce the CoRoT-2 spectrum if the planet exhibits line emission from CO at 4.5 mm, caused by tidal-induced mass loss. However, the viability of that hypothesis is questionable because the emitting region cannot be more than about 30% larger than the planet's transit radius, based on the ingress and egress times at eclipse. An alternative possibility to account for the spectrum of CoRoT-2 is an additional opacity source that acts strongly at wavelengths less than 5 mm, heating the upper atmosphere while allowing the deeper atmosphere seen at 8 mm to remain cooler. We obtain a similar result as Gillon et al. for the phase of the secondary eclipse of CoRoT-2, implying an eccentric orbit with e cos(w) = .0.0030 ± 0.0004.

 

 

Dért, J.-M., Sing, D., Vidal-Madjar, A., Héard, G., Ehrenreich, D., Lecavelier Des Etangs, A., Parmentier, V., Ferlet, R., Henry, G.W., 2011, "Transit spectrophotometry of the exoplanet HD 189733b. II. New Spitzer observations at 3.6 ?m," Astronomy and Astrophysics, 526, 12.

 

       Context. We present a new primary transit observation of the hot-jupiter obtained at 3.6 μm with the Infrared Array Camera (IRAC) onboard the Spitzer Space Telescope. Previous measurements at 3.6 microns suffered from strong systematics, and conclusions could hardly be obtained with confidence on the water detection by comparison of the 3.6 and 5.8 microns observations. 

Aims: We aim at constraining the atmospheric structure and composition of the planet and improving previously derived parameters. 

Methods: We use a high-S/N Spitzer photometric transit light curve to improve the precision of the near infrared radius of the planet at 3.6 μm. The observation has been performed using high-cadence time series integrated in the subarray mode. We are able to derive accurate system parameters, including planet-to-star radius ratio, impact parameter, scale of the system, and central time of the transit from the fits of the transit light curve. We compare the results with transmission spectroscopic models and with results from previous observations at the same wavelength. 

Results: We obtained the following system parameters of R_p/R_star = 0.15566^+0.00011_-0.00024, b = 0.661^+0.0053_-0.0050, and a/R_star = 8.925^+0.0490_-0.0523 at 3.6 μm. These measurements are three times more accurate than previous studies at this wavelength because they benefit from greater observational efficiency and less statistic and systematic errors. Nonetheless, we find that the radius ratio has to be corrected for stellar activity and present a method to do so using ground-based long-duration photometric follow-up in the V-band. The resulting planet-to-star radius ratio corrected for the stellar variability agrees with our previous measurement obtained in the same bandpass. We also discuss that water vapour could not be detected by a comparison of the planetary radius measured at 3.6 and 5.8 μm, because the radius measured at 3.6 μm is affected by absorption by other species, possibly Rayleigh scattering by haze.

 

 

 

Dominik, M., 2011, "Planetary mass function and planetary systems," Monthly Notices of the Royal Astronomical Society, 411, 2-8.

 

       With planets orbiting stars, a planetary mass function should not be seen as a low-mass extension of the stellar mass function, but a proper formalism needs to take care of the fact that the statistical properties of planet populations are linked to the properties of their respective host stars. This can be accounted for by describing planet populations by means of a differential planetary mass-radius-orbit function, which together with the fraction of stars with given properties that are orbited by planets and the stellar mass function allows the derivation of all statistics for any considered sample. These fundamental functions provide a framework for comparing statistics that result from different observing techniques and campaigns which all have their very specific selection procedures and detection efficiencies. Moreover, recent results both from gravitational microlensing campaigns and radial-velocity surveys of stars indicate that planets tend to cluster in systems rather than being the lonely child of their respective parent star. While planetary multiplicity in an observed system becomes obvious with the detection of several planets, its quantitative assessment however comes with the challenge to exclude the presence of further planets. Current exoplanet samples begin to give us first hints at the population statistics, whereas pictures of planet parameter space in its full complexity call for samples that are 2-4 orders of magnitude larger. In order to derive meaningful statistics, however, planet detection campaigns need to be designed in such a way that well-defined fully deterministic target selection, monitoring and detection criteria are applied. The probabilistic nature of gravitational microlensing makes this technique an illustrative example of all the encountered challenges and uncertainties.

 

 

 

Dumusque, X., Udry, S., Lovis, C., Santos, N.C., Monteiro, M.J.P.F.G., 2011, "Planetary detection limits taking into account stellar noise. I. Observational strategies to reduce stellar oscillation and granulation effects," Astronomy and Astrophysics, 525, 140.

 

       Context. Stellar noise produced by oscillations, granulation phenomena (granulation, mesogranulation, and supergranulation), and activity affects radial velocity measurements. The signature of the corresponding effect in radial velocity is small, around the meter-per-second, but already too large for the detection of Earth-mass planets in habitable zones.

Aims: We address the important role played by observational strategies in averaging out the radial velocity signature of stellar noise. We also derive the planetary mass detection limits expected in the presence of stellar noise.

 

Methods: We start with HARPS asteroseismology measurements for four stars (b Hyi, a Cen A, m Ara, and t Ceti) available in the ESO archive and very precise measurements of a Cen B. This sample covers different spectral types from G2 to K1 and different evolutionary stages, from subgiant to dwarf stars. Since data span between 5 and 8 days, only stellar noise sources with timescales shorter than this time span will be extracted from these observations. Therefore, we are able to study oscillation modes and granulation phenomena without being significantly affected by activity noise present on longer timescales. For those five stars, we generate synthetic radial velocity measurements after fitting the corresponding models of stellar noise in Fourier space. These measurements allow us to study the radial velocity variation due to stellar noise for different observational strategies as well as the corresponding planetary mass detection limits.

 

Results: Applying three measurements per night of 10 min exposure each, 2 h apart, seems to most efficiently average out the stellar noise considered. For quiet K1V stars such as a Cen B, this strategy allows us to detect planets of about three times the mass of Earth with an orbital period of 200 days, corresponding to the habitable zone of the star. Moreover, our simulations suggest that planets smaller than typically 5 M_Earthcan be detected with HARPS over a wide range of separations around most non-active solar-type dwarfs. Since activity is not yet included in our simulation, these detection limits correspond to a case, which exists, where the host star has few magnetic features and stellar noise is dominated by oscillation modes and granulation phenomena. For our star sample, a trend between spectral type and surface gravity and the level of radial velocity variation is also identified by our simulations.

 

 

Enoch, B., Cameron, A.C., Anderson, D.R., Lister, T.A., Hellier, C., Maxted, P.F.L., Queloz, D., Smalley, B., Triaud, A.H.M.J., West, R.G., Brown, D.J.A., Gillon, M., Hebb, L., Lendl, M., Parley, N., Pepe, F., Pollacco, D., Segransan, D., Simpson, E., Street, R.A., Udry, S., 2011, "WASP-25b: a 0.6 MJ planet in the Southern hemisphere," Monthly Notices of the Royal Astronomical Society, 410, 1631-1636.

 

       We report the detection of a 0.6 M_J extrasolar planet by WASP-South, WASP-25b, transiting its solar-type host star every 3.76 d. A simultaneous analysis of the WASP, FTS and Euler photometry and CORALIE spectroscopy yields a planet of R_p= 1.22 R_J and M_p= 0.58 M_J around a slightly metal-poor solar-type host star, [Fe/H]=- 0.05 ± 0.10, of R_*= 0.92 R_ȯ and M_*= 1.00 M_ȯ. WASP-25b is found to have a density of ρ_p= 0.32 ρ_J, a low value for a sub-Jupiter mass planet. We investigate the relationship of planetary radius to planetary equilibrium temperature and host star metallicity for transiting exoplanets with a similar mass to WASP-25b, finding that these two parameters explain the radii of most low-mass planets well.

 

 

 

Faedi, F., West, R.G., Burleigh, M.R., Goad, M.R., Hebb, L., 2011, "Detection limits for close eclipsing and transiting substellar and planetary companions to white dwarfs in the WASP survey," Monthly Notices of the Royal Astronomical Society, 410, 899-911.

 

       We have performed extensive simulations to explore the possibility of detecting eclipses and transits of close, substellar and planetary companions to white dwarfs in WASP (the UK Wide-Angle Search for Planets) light curves. Our simulations cover companions ~0.3 < R_pl < 12 R? and orbital periods 2 < P < 15 d, equivalent to orbital radii 0.003 < a < 0.1 au. For Gaussian random noise, WASP is sensitive to transits by companions as small as the Moon orbiting a V≃ 12 white dwarf. For fainter white dwarfs, WASP is sensitive to increasingly larger radius bodies. However, in the presence of correlated noise structure in the light curves, the sensitivity drops, although Earth-sized companions remain detectable, in principle, even in low signal-to-noise data. Mars-sized, and even Mercury-sized, bodies yield reasonable detection rates in high-quality light curves with little residual noise. We searched for eclipses and transit signals in long-term light curves of a sample of 194 white dwarfs resulting from a cross-correlation of the McCook & Sion catalogue and the WASP archive. No evidence for eclipsing or transiting substellar and planetary companions was found. We used this non-detection and results from our simulations to place tentative upper limits to the frequency of such objects in close orbits at white dwarfs. While only weak limits can be placed on the likely frequency of Earth-sized or smaller companions, brown dwarfs and gas giants (radius ≈R_jup) with periods <0.1-0.2 d must certainly be rare (<10 per cent). More stringent constraints likely require significantly larger white dwarf samples, higher observing cadence and continuous coverage. The short duration of eclipses and transits of white dwarfs compared to the cadence of WASP observations appears to be one of the main factors limiting the detection rate in a survey optimized for planetary transits of main-sequence stars

 

 

Fernáez, J.A., 2011, "On the Existence of a Distant Solar Companion and its Possible Effects on the Oort Cloud and the Observed Comet Population," The Astrophysical Journal, 726, 33.

 

       We analyze the possible existence and detection of a distant massive solar companion. Such an object.if it exists.should be very faint in the visible, so its direct detection might depend on current or future infrared sky surveys, like WISE. Alternatively, its presence could be uncovered through its perturbing effects on nearby objects such as, for instance, Oort Cloud comets (OCCs). We then estimate how putative solar companions of different masses and semimajor axes can perturb nearby OCCs causing an enhancement of the comet flux along the companion's path. We find that a companion of 5 Jupiter masses (M_J ) can produce a signature detectable with the current record of observed new comets, provided that the Oort Cloud contains a dense inner core of comets and that the distance of the perturber is smaller than ~2 ×10⁴ AU. A 1 M_J perturber can produce a signature detectable in the current record only if its distance were smaller than ~(2-3) ×10³ AU. The sample of discovered new comets is found to be two orders of magnitude too small to show a signature caused by a Neptune-mass companion at any distance above ~10³ AU to a significant level. We also estimate that the Oort Cloud will withstand the steady perturbing effects by a massive solar companion over the solar system age, with only a minor erosion, unless the companion had a mass >~ few M_J , and were at a distance <~ few 10³ AU.

 

 

Funk, B., Libert, A.-S., Sü., Pilat-Lohinger, E., 2011, "On the influence of the Kozai mechanism in habitable zones of extrasolar planetary systems," Astronomy and Astrophysics, 526, 98.

 

       Aims: We investigate the long-term evolution of inclined test particles representing a small Earth-like body with negligible gravitational effects (hereafter called massless test-planets) in the restricted three-body problem, and consisting of a star, a gas giant, and a massless test-planet. The test-planet is initially on a circular orbit and moves around the star at distances closer than the gas giant. The aim is to show the influences of the eccentricity and the mass of the gas giant on the dynamics, for various inclinations of the test-planet, and to investigate in more detail the Kozai mechanism in the elliptic problem.

 

Methods: We performed a parametric study, integrating the orbital evolution of test particles whose initial conditions were distributed on the semi-major axis - inclination plane. The gas giant's initial eccentricity was varied. For the calculations, we used the Lie integration method and in some cases the Bulirsch-Stoer algorithm. To analyze the results, the maximum eccentricity and the Lyapunov characteristic indicator were used. All integrations were performed for 10⁵ periods of the gas giant.

 

Results: Our calculations show that inclined massless test-planets can be in stable configurations with gas giants on either circular or elliptic orbits. The higher the eccentricity of the gas giant, the smaller the possible range in semi-major axis for the test-planet. For gas giants on circular orbits, our results illustrate the well-known results associated with the Kozai mechanism, which do not allow stable orbits above a critical inclination of approximately 40°. For gas giants on eccentric orbits, the dynamics is quite similar, and the massless companion exhibits limited variations in eccentricity. In addition, we identify a region around 35° consisting of long-time stable, low eccentric orbits. We show that these results are also valid for Earth-mass companions, therefore they can be applied to extrasolar systems: for instance, the extrasolar planetary system HD 154345 can possess a 35° degree inclined, nearly circular, Earth-mass companion in the habitable zone.

 

 

Funk, B., Schwarz, R., Dvorak, R., Roth, M., 2011, "Exchange orbits: a possible application to extrasolar planetary systems?," Monthly Notices of the Royal Astronomical Society, 410, 455-460.

 

       Among the 48 known multiplanetary systems, some are in mean-motion resonances (in most cases in the 2:1 mean-motion resonance). Although until now no extrasolar planetary systems have been found in a 1:1 mean-motion resonance, many studies are dealing with this configuration. Besides the well-known motion of the Trojan asteroids, further possibilities exist for stable configurations of planets or satellites in a 1:1 resonance. For one thing, we can find so-called exchange orbits in our Solar system (Janus and Epimetheus), where both Saturnian moons exchange the values of their semi-major axes (exchange-a configuration) when approaching each other. In addition, we can also find similar behaviour for two planets on orbits with the same semi-major axis, but with different eccentricities; here an exchange of eccentricities takes place (exchange-e configuration). In this work we focused on the second possibility and performed a parameter study by varying the initial conditions (mass and eccentricity) of two planets on exchange-e orbits. By means of an extensive numerical study, we can find a wide variety of initial conditions leading to long-term stable orbits.

 

 

Gardner, E., Nurmi, P., Flynn, C., Mikkola, S., 2011, "The effect of the solar motion on the flux of long-period comets," Monthly Notices of the Royal Astronomical Society, 411, 947-954.

 

       The long-term dynamics of Oort cloud comets are studied under the influence of both the radial and the vertical components of the Galactic tidal field. Sporadic dynamical perturbation processes, such as passing stars, are ignored since we aim to study the influence of just the axisymmetric Galactic tidal field on the cometary motion and how it changes in time. We use a model of the Galaxy with a disc, bulge and dark halo, and a local disc density and disc scalelength constrained to fit the best available observational constraints. By integrating a few million of cometary orbits over 1 Gyr, we calculate the time variable flux of Oort cloud comets that enter the inner Solar system for the cases of a constant Galactic tidal field and a realistically varying tidal field, which is a function of the Sun's orbit. The applied method calculates the evolution of the comets by using first-order averaged mean elements. We find that the periodicity in the cometary flux is complicated and quasi-periodic. The amplitude of the variations in the flux is of the order of 30 per cent. The radial motion of the Sun is the chief cause of this behaviour, and should be taken into account when the Galactic influence on the Oort cloud comets is studied.

 

 

Gillon, M., Bonfils, X., Demory, B.-O., Seager, S., Deming, D., Triaud, A.H.M.J., 2011, "An educated search for transiting habitable planets:. Targetting M dwarfs with known transiting planets," Astronomy and Astrophysics, 525, 32.

 

       Because the planets of a system form in a flattened disk, they are expected to share similar orbital inclinations at the end of their formation. The high-precision photometric monitoring of stars known to host a transiting planet could thus reveal the transits of one or more other planets. We investigate here the potential of this approach for the M dwarf GJ 1214 that hosts a transiting super-Earth. For this system, we infer the transit probabilities as a function of orbital periods. Using Monte-Carlo simulations we address both the cases for fully coplanar and for non-coplanar orbits, with three different choices of inclinations distribution for the non-coplanar case. GJ 1214 reveals to be a very promising target for the considered approach. Because of its small size, a ground-based photometric monitoring of this star could detect the transit of a habitable planet as small as the Earth, while a space-based monitoring could detect any transiting habitable planet down to the size of Mars. The mass measurement of such a small planet would be out of reach for current facilities, but we emphasize that a planet mass would not be needed to confirm the planetary nature of the transiting object. Furthermore, the radius measurement combined with theoretical arguments would help us to constrain the structure of the planet.

 

 

Gong, Y.-X., Wu, X.-M., 2011, "GENERAL Post-post-Newtonian deflection of light ray in multiple systems with PPN parameters," Chinese Physics B, 20, 0403.

 

       The post-Newtonian scheme in multiple systems with post-Newtonian parameters presented by Klioner and Soffel is extended to the post-post-Newtonian (PPN) order for light propagation problem in the solar system. Under considering the solar system experiment requirement, a new parameter e is introduced. This extension does not change the virtue of the scheme on the linear partial differential equations of the potential and vector potential mentioned in previous work. Furthermore, this extension is based on the former work done by Richter and Matzner in one global system theory. As an application, we also consider the deflection of light ray in the global coordinates. And the deflection angle of light ray is obtained with post-Newtonian parameters.

 

 

 

Gregory, P.C., 2011, "Bayesian exoplanet tests of a new method for MCMC sampling in highly correlated model parameter spaces," Monthly Notices of the Royal Astronomical Society, 410, 94-110.

 

       The Markov chain Monte Carlo (MCMC) method is a powerful technique for facilitating Bayesian non-linear model fitting. In many cases, the MCMC exploration of the parameter space is very inefficient, because the model parameters are highly correlated. Differential evolution MCMC is one technique that addresses this problem by employing multiple parallel chains. We present a new method that automatically achieves efficient MCMC sampling in highly correlated parameter spaces, which does not require additional chains to accomplish this. It was designed to work with an existing hybrid MCMC (HMCMC) algorithm, which incorporates parallel tempering, simulated annealing and genetic cross-over operations. These features, together with the new correlated parameter sampler, greatly facilitate the detection of a global minimum in c². The new HMCMC algorithm is very general in scope. Two tests of the algorithm are described employing (a) exoplanet precision radial velocity (RV) data and (b) simulated space astrometry data. The latter test explores the accuracy of parameter estimates obtained with the Bayesian HMCMC algorithm on the assumed astrometric noise.

 

 

Grumiller, D., 2011, "Erratum: Model for Gravity at Large Distances [Phys. Rev. Lett. 105, 211303 (2010)]," Physical Review Letters, 106, 39901.

 

       We construct an effective model for gravity of a central object at large scales. To leading order in the large radius expansion we find a cosmological constant, a Rindler acceleration, a term that sets the physical scales and subleading terms. All these terms are expected from general relativity, except for the Rindler term. The latter leads to an anomalous acceleration in geodesics of test-particles.

 

 

Hartman, J.D., Bakos, G.Á, Kipping, D.M., Torres, G., Ková, G., Noyes, R.W., Latham, D.W., Howard, A.W., Fischer, D.A., Johnson, J.A., Marcy, G.W., Isaacson, H., Quinn, S.N., Buchhave, L.A., Bé, B., Sasselov, D.D., Stefanik, R.P., Esquerdo, G.A., Everett, M., Perumpilly, G., Lár, J., Papp, I., Sá, P., 2011, "HAT-P-26b: A Low-density Neptune-mass Planet Transiting a K Star," The Astrophysical Journal, 728, 138.

 

       We report the discovery of HAT-P-26b, a transiting extrasolar planet orbiting the moderately bright V = 11.744 K1 dwarf star GSC 0320-01027, with a period P = 4.234516 ± 0.000015 days, transit epoch T_c = 2455304.65122 ± 0.00035 (BJD; Barycentric Julian dates throughout the paper are calculated from Coordinated Universal Time (UTC)), and transit duration 0.1023 ± 0.0010 days. The host star has a mass of 0.82 ± 0.03 M _sun, radius of 0.79^+0.10 _-0.04 R _sun, effective temperature 5079 ± 88 K, and metallicity [Fe/H] = -0.04 ± 0.08. The planetary companion has a mass of 0.059 ± 0.007 M _J, and radius of 0.565^+0.072 _-0.032 R _J yielding a mean density of 0.40 ± 0.10 g cm^-3. HAT-P-26b is the fourth Neptune-mass transiting planet discovered to date. It has a mass that is comparable to those of Neptune and Uranus, and slightly smaller than those of the other transiting Super-Neptunes, but a radius that is ~65% larger than those of Neptune and Uranus, and also larger than those of the other transiting Super-Neptunes. HAT-P-26b is consistent with theoretical models of an irradiated Neptune-mass planet with a 10 M _⊕ heavy element core that comprises >~50% of its mass with the remainder contained in a significant hydrogen-helium envelope, though the exact composition is uncertain as there are significant differences between various theoretical models at the Neptune-mass regime. The equatorial declination of the star makes it easily accessible to both Northern and Southern ground-based facilities for follow-up observations.

 

 

Hartman, J.D., Bakos, G.Á, Sato, B., Torres, G., Noyes, R.W., Latham, D.W., Ková, G., Fischer, D.A., Howard, A.W., Johnson, J.A., Marcy, G.W., Buchhave, L.A., Fü G., Perumpilly, G., Bé, B., Stefanik, R.P., Sasselov, D.D., Esquerdo, G.A., Everett, M., Csubry, Z., Lár, J., Papp, I., Sá, P., 2011, "HAT-P-18b and HAT-P-19b: Two Low-density Saturn-mass Planets Transiting Metal-rich K Stars," The Astrophysical Journal, 726, 52.

 

       We report the discovery of two new transiting extrasolar planets. HAT-P-18b orbits the V = 12.759 K2 dwarf star GSC 2594-00646, with a period P = 5.508023 ± 0.000006 days, transit epoch T_c = 2454715.02174 ± 0.00020 (BJD), and transit duration 0.1131 ± 0.0009 days. The host star has a mass of 0.77 ± 0.03 M _sun, radius of 0.75 ± 0.04 R _sun, effective temperature 4803 ± 80 K, and metallicity [Fe/H] = +0.10 ± 0.08. The planetary companion has a mass of 0.197 ± 0.013 M _Jand radius of 0.995 ± 0.052 R _J, yielding a mean density of 0.25 ± 0.04 g cm^-3. HAT-P-19b orbits the V = 12.901 K1 dwarf star GSC 2283-00589, with a period P = 4.008778 ± 0.000006 days, transit epoch T_c = 2455091.53417 ± 0.00034 (BJD), and transit duration 0.1182 ± 0.0014 days. The host star has a mass of 0.84 ± 0.04 M _sun, radius of 0.82 ± 0.05 R _sun, effective temperature 4990 ± 130 K, and metallicity [Fe/H] = +0.23 ± 0.08. The planetary companion has a mass of 0.292 ± 0.018 M _J and radius of 1.132 ± 0.072 R _J, yielding a mean density of 0.25 ± 0.04 g cm^-3. The radial velocity residuals for HAT-P-19 exhibit a linear trend in time, which indicates the presence of a third body in the system. Comparing these observations with theoretical models, we find that HAT-P-18b and HAT-P-19b are each consistent with a hydrogen-helium-dominated gas giant planet with negligible core mass. HAT-P-18b and HAT-P-19b join HAT-P-12b and WASP-21b in an emerging group of low-density Saturn-mass planets, with negligible inferred core masses. However, unlike HAT-P-12b and WASP-21b, both HAT-P-18b and HAT-P-19b orbit stars with super-solar metallicity. This calls into question the heretofore suggestive correlation between the inferred core mass and host star metallicity for Saturn-mass planets.

 

 

Hartung, J., Steinhoff, J., 2011, "Next-to-leading order spin-orbit and spin(a)-spin(b) Hamiltonians for n gravitating spinning compact objects," Physical Review D, 83, 44008.

 

       We derive the post-Newtonian next-to-leading order conservative spin-orbit and spin(a)-spin(b) gravitational interaction Hamiltonians for arbitrary many compact objects. The spin-orbit Hamiltonian completes the knowledge of Hamiltonians up to and including 2.5 post Newtonian for the general relativistic three-body problem. The new Hamiltonians include highly nontrivial three-body interactions, in contrast to the leading order consisting of two-body interactions only. This may be important for the study of effects like Kozai resonances in mergers of black holes with binary black holes. The derivation was done via two independent methods giving fully consistent results.

 

 

 

Hernáez-Mena, C., Benet, L., 2011, "Statistics and universality in simplified models of planetary formation," Monthly Notices of the Royal Astronomical Society, 21.

 

       In this paper, we modify Laskar.s simplified model of planetary evolution and accretion to account for the full conservation of the total angular momentum of the system, and extend it to incorporate an accretion probability that depends on the mass and relative velocity of the colliding particles. We present statistical results for the mass and eccentricity of the planets formed, in terms of their semimajor axes, for a large number of realizations of different versions of the model. In particular, we find that by combining the mass-dependent accretion probability and the velocity-selection mechanism, the planets formed display a systematic occurrence at specific locations. By introducing properly scaled variables, our results are universal with respect to the total angular momentum of the system, the mass of the planetesimal disc and the mass of the central star.

 

 

Horch, E.P., Gomez, S.C., Sherry, W.H., Howell, S.B., Ciardi, D.R., Anderson, L.M., van Altena, W.F., 2011, "Observations of Binary Stars with the Differential Speckle Survey Instrument. II. Hipparcos Stars Observed in 2010 January and June," The Astronomical Journal, 141, 45.

 

       The results of 497 speckle observations of Hipparcos stars and selected other targets are presented. Of these, 367 were resolved into components and 130 were unresolved. The data were obtained using the Differential Speckle Survey Instrument at the WIYN 3.5 m Telescope. (The WIYN Observatory is a joint facility of the University of Wisconsin-Madison, Indiana University, Yale University, and the National Optical Astronomy Observatories.) Since the first paper in this series, the instrument has been upgraded so that it now uses two electron-multiplying CCD cameras. The measurement precision obtained when comparing to ephemeris positions of binaries with very well known orbits is approximately 1-2 mas in separation and better than 0.6° in position angle. Differential photometry is found to be in very good agreement with Hipparcos measures in cases where the comparison is most relevant. We derive preliminary orbits for two systems.

 

 

Howard, A.W., Johnson, J.A., Marcy, G.W., Fischer, D.A., Wright, J.T., Henry, G.W., Isaacson, H., Valenti, J.A., Anderson, J., Piskunov, N.E., 2011, "The NASA-UC Eta-Earth Program. II. A Planet Orbiting HD 156668 with a Minimum Mass of Four Earth Masses," The Astrophysical Journal, 726, 73.

 

       We report the discovery of HD 156668 b, an extrasolar planet with a minimum mass of M_P sin i = 4.15 M _⊕. This planet was discovered through Keplerian modeling of precise radial velocities from Keck-HIRES and is the second super-Earth to emerge from the NASA-UC Eta-Earth Survey. The best-fit orbit is consistent with circular and has a period of P = 4.6455 days. The Doppler semi-amplitude of this planet, K = 1.89 m s^-1, is among the lowest ever detected, on par with the detection of GJ 581 e using HARPS. A longer period (P ≈ 2.3 years), low-amplitude signal of unknown origin was also detected in the radial velocities and was filtered out of the data while fitting the short-period planet. Additional data are required to determine if the long-period signal is due to a second planet, stellar activity, or another source. Photometric observations using the Automated Photometric Telescopes at Fairborn Observatory show that HD 156668 (an old, quiet K3 dwarf) is photometrically constant over the radial velocity period to 0.1 mmag, supporting the existence of the planet. No transits were detected down to a photometric limit of ~3 mmag, ruling out transiting planets dominated by extremely bloated atmospheres, but not precluding a transiting solid/liquid planet with a modest atmosphere.

 

 

Hwang, Y., Lee, B.-S., Kim, H., Kim, J., 2011, "Orbit determination performances using single- and double-differenced methods: SAC-C and KOMPSAT-2," Advances in Space Research, 47, 138-148.

 

       In this paper, Global Positioning System-based (GPS) Orbit Determination (OD) for the KOrea-Multi-Purpose-SATellite (KOMPSAT)-2 using single- and double-differenced methods is studied. The requirement of KOMPSAT-2 orbit accuracy is to allow 1 m positioning error to generate 1-m panchromatic images. KOMPSAT-2 OD is computed using real on-board GPS data. However, the local time of the KOMPSAT-2 GPS receiver is not synchronized with the zero fractional seconds of the GPS time internally, and it continuously drifts according to the pseudorange epochs. In order to resolve this problem, an OD based on single-differenced GPS data from the KOMPSAT-2 uses the tagged time of the GPS receiver, and the accuracy of the OD result is assessed using the overlapping orbit solution between two adjacent days. The clock error of the GPS satellites in the KOMPSAT-2 single-differenced method is corrected using International GNSS Service (IGS) clock information at 5-min intervals. KOMPSAT-2 OD using both double- and single-differenced methods satisfies the requirement of 1-m accuracy in overlapping three dimensional orbit solutions. The results of the SAC-C OD compared with JPL.s POE (Precise Orbit Ephemeris) are also illustrated to demonstrate the implementation of the single- and double-differenced methods using a satellite that has independent orbit information available for validation.

 

 

Ibgui, L., Spiegel, D.S., Burrows, A., 2011, "Explorations into the Viability of Coupled Radius-orbit Evolutionary Models for Inflated Planets," The Astrophysical Journal, 727, 75.

 

       The radii of some transiting extrasolar giant planets are larger than would be expected by the standard theory. We address this puzzle with the model of coupled radius-orbit tidal evolution developed by Ibgui & Burrows. The planetary radius is evolved self-consistently with orbital parameters, under the influence of tidal torques and tidal dissipation in the interior of the planet. A general feature of this model, which we have previously demonstrated in the generic case, is that a possible transient inflation of the planetary radius can temporarily interrupt its standard monotonic shrinking and can lead to the inflated radii that we observe. Importantly, we demonstrate that the use of a constant time lag model for the orbital evolution does not improve the accuracy of the evolutionary calculations. First, though formulated in a closed form by the equations of Hut, it is not valid at large eccentricities, as for the constant phase lag model truncated at the second order in eccentricity that we adopt; ambiguities in tidal theories are perhaps the most significant source of uncertainty in evolutionary calculations. Second, we find evolutionary tracks that fit within the 1σ error bars, the radius, the eccentricity, and the semimajor axis of HD 209458b in its current estimated age range, using the constant time lag model, as we find fitting tracks with the constant phase lag model. Both models show that a bloated planet with a circular orbit may still be inflated, due to thermal inertia. We have modified our constant phase lag model to include an orbital period dependence of the tidal dissipation factor in the star, Q'_* µ P ^γ, -1 <= γ <= 1. For some inflated planets (WASP-6b and WASP-15b), we find fitting tracks; for another (TrES-4), we do not; and for others (WASP-4b and WASP-12b), we find fitting tracks, but our model might imply that we are observing the planets at a special time. Finally, we stress a 2-3 order-of-magnitude timescale uncertainty of the inspiraling phase of the planet into its host star, arising from uncertainties in Q'_*.

 

Iorio, L., 2011, "Classical and relativistic long-term time variations of some observables for transiting exoplanets," Monthly Notices of the Royal Astronomical Society, 411, 167-183.

 

       We analytically work out the long-term, i.e. averaged over one orbital revolution, time variations  of some direct observable quantities Y induced by classical and general relativistic dynamical perturbations of the two-body point-like Newtonian acceleration in the case of transiting exoplanets moving along elliptic orbits. More specifically, the observables Y with which we deal are the transit duration Δt_d, the radial velocity V_ρ, the time interval Δt_ecl between primary and secondary eclipses, and the time interval P_tr between successive primary transits. The dynamical effects considered are the centrifugal oblateness of both the star and the planet, their tidal bulges mutually raised on each other, a distant third-body X and general relativity (both Schwarzschild and Lense.Thirring). We take into account the effects due to the perturbations of all the Keplerian orbital elements involved in a consistent and uniform way. First, we explicitly compute their instantaneous time variations due to the dynamical effects considered and substitute them in the general expression for the instantaneous change of Y; then, we take the overall average over one orbital revolution of the so-obtained instantaneous rate specialized to the perturbations considered. In contrast, previous published works have often employed somewhat .hybrid. expressions, in which the secular precession of, typically, the periastron only is straightforwardly inserted into instantaneous formulas. The transit duration is affected neither by the general relativistic Schwarzschild-type nor by the classical tidal effects, while the bodies. centrifugal oblatenesses, a distant third-body X and the general relativistic Lense.Thirring-type perturbations induce non-vanishing long-term, harmonic effects on Δt_d also for circular orbits. For exact edge-on configurations they vanish. Both V_ρ and Δt_ecl experience non-vanishing long-term, harmonic variations, caused by all the perturbations considered, only for non-circular orbits. Also P_tr is affected by all of them with long-term signatures, but they do not vanish for circular orbits. Numerical evaluations of the obtained results are given for a typical star.planet scenario and compared with the expected observational accuracies over a time-span τ= 10 yr long. Also graphical investigations of the dependence of the effects considered on the semimajor axis and the eccentricity are presented. Our results are, in principle, valid also for other astronomical scenarios. They may allow, e.g., for designing various tests of gravitational theories with natural and artificial bodies in our Solar system.    

 

Iorio, L., 2011, "Classical and relativistic node precessional effects in WASP-33b and perspectives for detecting them," Astrophysics and Space Science, 331, 485-496.

 

       WASP-33 is a fast rotating, main sequence star which hosts a hot Jupiter moving along a retrograde and almost polar orbit with semi-major axis a=0.02 au and eccentricity provisionally set to e=0. The quadrupole mass moment J₂^{star} and the proper angular momentum S _⋆ of the star are 1900 and 400 times, respectively, larger than those of the Sun. Thus, huge classical and general relativistic non-Keplerian orbital effects should take place in such a system. In particular, the large inclination Ψ_⋆ of the orbit of WASP-33b to the star's equator allows to consider the node precession dot{Ω} and the related time variation dt _d / dt of the transit duration t _d . The WASP-33b node rate due to J₂^{star} is 9×0⁹ times larger than the same effect for Mercury induced by the Sun's oblateness, while the general relativistic gravitomagnetic node precession is 3×0⁵ times larger than the Lense-Thirring effect for Mercury due to the Sun's rotation. We also consider the effect of the centrifugal oblateness of the planet itself and of a putative distant third body X. The magnitudes of the induced time change in the transit duration are of the order of 3×0^-6,2×0^-7,8×0^-9 for J₂^{star}, the planet's rotational oblateness and general relativity, respectively. A yet undiscovered planet X with the mass of Jupiter orbiting at more than 1 au would induce a transit duration variation of less than 4×0^-9. A conservative evaluation of the accuracy in measuring dt _d / dt over 10 yr points towards ≈10^-8. The analysis presented here will be applicable also to other exoplanets with similar features if and when they will ne discovered.

 

 

Iorio, L., Lichtenegger, H.I.M., Ruggiero, M.L., Corda, C., 2011, "Phenomenology of the Lense-Thirring effect in the solar system," Astrophysics and Space Science, 331, 351-395.

 

       Recent years have seen increasing efforts to directly measure some aspects of the general relativistic gravitomagnetic interaction in several astronomical scenarios in the solar system. After briefly overviewing the concept of gravitomagnetism from a theoretical point of view, we review the performed or proposed attempts to detect the Lense-Thirring effect affecting the orbital motions of natural and artificial bodies in the gravitational fields of the Sun, Earth, Mars and Jupiter. In particular, we will focus on the evaluation of the impact of several sources of systematic uncertainties of dynamical origin to realistically elucidate the present and future perspectives in directly measuring such an elusive relativistic effect.

 

 

Ireland, M.J., Kraus, A., Martinache, F., Law, N., Hillenbrand, L.A., 2011, "Two Wide Planetary-mass Companions to Solar-type Stars in Upper Scorpius," The Astrophysical Journal, 726, 113.

 

       At wide separations, planetary-mass and brown dwarf companions to solar-type stars occupy a curious region of parameter space not obviously linked to binary star formation or solar system scale planet formation. These companions provide insight into the extreme case of companion formation (either binary or planetary), and due to their relative ease of observation when compared to close companions, they offer a useful template for our expectations of more typical planets. We present the results from an adaptive optics imaging survey for wide (~50-500 AU) companions to solar-type stars in Upper Scorpius. We report one new discovery of a ~14 M_J companion around GSC 06214.00210and confirm that the candidate planetary-mass companion 1RXS J160929.1.210524 detected by Lafreniè et al. is in fact comoving with its primary star. In our survey, these two detections correspond to ~4% of solar-type stars having companions in the 6-20 M _Jmass and ~200-500 AU separation range. This figure is higher than would be expected if brown dwarfs and planetary-mass companions were drawn from an extrapolation of the binary mass function. Finally, we discuss implications for the formation of these objects.

 

Ji, J., Jin, S., Tinney, C.G., 2011, "Forming Close-in Earth-like Planets Via a Collision-merger Mechanism in Late-stage Planet Formation," The Astrophysical Journal, 727, L5.

 

       The large number of exoplanets found to orbit their host stars in very close orbits have significantly advanced our understanding of the planetary formation process. It is now widely accepted that such short-period planets cannot have formed in situ, but rather must have migrated to their current orbits from a formation location much farther from their host star. In the late stages of planetary formation, once the gas in the protoplanetary disk has dissipated and migration has halted, gas giants orbiting in the inner disk regions will excite planetesimals and planetary embryos, resulting in an increased rate of orbital crossings and large impacts. We present the results of dynamical simulations for planetesimal evolution in this later stage of planet formation. We find that a mechanism is revealed by which the collision-merger of planetary embryos can kick terrestrial planets directly into orbits extremely close to their parent stars.

 

 

Jin, S., Zhang, L.J., Tapley, B.D., 2011, "The understanding of length-of-day variations from satellite gravity and laser ranging measurements," Geophysical Journal International, 184, 651-660.

 

       SUMMARYThe change in the rate of the Earth's rotation, length-of-day (LOD), is principally the result of movement and redistribution of mass in the Earth's atmosphere, oceans and hydrosphere. Numerous studies on the LOD excitations have been made from climatological/hydrological assimilation systems and models of the general circulation of the ocean. However, quantitative assessment and understanding of the contributions to the LOD remain unclear due mainly to the lack of direct global observations. In this paper, the total Earth's surface fluids mass excitations to the LOD at seasonal and intraseasonal timescales are investigated from the Jet Propulsion Laboratory Estimating Circulation and Climate of the Ocean (ECCO) model, the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis and the European Center for Medium-Range Weather Forecasts (ECMWF) Re-analysis (ERA)-Interim, GRACE-derived surface fluids mass and the spherical harmonics coefficient C₂₀ from the satellite laser ranging (SLR) as well as combined GRACE+SLR solutions, respectively. Results show that the GRACE and the combined GRACE and SLR solutions better explain the geodetic residual LOD excitations at annual and semi-annual timescales. For less than 1 yr timescales, GRACE-derived mass is worse to explain the geodetic residuals, whereas SLR agrees better with the geodetic residuals. However, the combined GRACE and SLR results are much improved in explaining the geodetic residual excitations at intraseasonal scales.

 

 

Jones, D.L., Fomalont, E., Dhawan, V., Romney, J., Folkner, W.M., Lanyi, G., Border, J., Jacobson, R.A., 2011, "Very Long Baseline Array Astrometric Observations of the Cassini Spacecraft at Saturn," The Astronomical Journal, 141, 29.

 

       The planetary ephemeris is an essential tool for interplanetary spacecraft navigation, studies of solar system dynamics (including, for example, barycenter corrections for pulsar timing ephemerides), the prediction of occultations, and tests of general relativity. We are carrying out a series of astrometric very long baseline interferometry observations of the Cassini spacecraft currently in orbit around Saturn, using the Very Long Baseline Array (VLBA). These observations provide positions for the center of mass of Saturn in the International Celestial Reference Frame (ICRF) with accuracies ~0.3 mas (1.5 nrad) or about 2 km at the average distance of Saturn. This paper reports results from eight observing epochs between 2006 October and 2009 April. These data are combined with two VLBA observations by other investigators in 2004 and a Cassini-based gravitational deflection measurement by Fomalont et al. in 2009 to constrain a new ephemeris (DE 422). The DE 422 post-fit residuals for Saturn with respect to the VLBA data are generally 0.2 mas, but additional observations are needed to improve the positions of all of our phase reference sources to this level. Over time we expect to be able to improve the accuracy of all three coordinates in the Saturn ephemeris (latitude, longitude, and range) by a factor of at least three. This will represent a significant improvement not just in the Saturn ephemeris but also in the link between the inner and outer solar system ephemerides and in the link to the inertial ICRF.

 

 

Kennedy, G.M., Wyatt, M.C., 2011, "Collisional evolution of irregular satellite swarms: detectable dust around Solar system and extrasolar planets," Monthly Notices of the Royal Astronomical Society, 135.

 

       Since the 1980s it has been becoming increasingly clear that the Solar system.s irregular satellites are collisionally evolved. The current populations are remnants of much more massive swarms that have been grinding away for billions of years. Here, we derive a general model for the collisional evolution of an irregular satellite swarm and apply it to the Solar system and extrasolar planets. The model uses a particle-in-a-box formalism and considers implications for the size distribution, which allows a connection between irregular satellite populations and predicted levels in the resulting dust cloud. Our model reproduces the Solar system.s complement of observed irregulars well, and suggests that the competition between grain-grain collisions and Poynting-Robertson (PR) drag helps set the fate of the dust. In collision-dominated swarms most dust is lost to interplanetary space or impacts the host planet, while PR-dominated grains spiral in towards the planet through the domain of regular satellites. Because swarm collision rates decrease over time the main dust sink can change with time, and may help unravel the accretion history of synchronously rotating regular satellites that show brightness asymmetries, such as Callisto and Iapetus. Some level of dust must be present on au scales around the Solar system.s giant planets if the irregular satellites are still grinding down, which we predict may be at detectable levels. We also use our model to predict whether dust produced by extrasolar circumplanetary swarms can be detected. Though designed with planets in mind, the coronagraphic instruments on James Webb Space Telescope (JWST) will have the ability to detect the dust generated by these swarms, which are most detectable around planets that orbit at many tens of au from the youngest stars. Because the collisional decay of swarms is relatively insensitive to planet mass, swarms can be much brighter than their host planets and allow discovery of Neptune-mass planets that would otherwise remain invisible. This dust could have been detected by Hubble Space Telescope Advanced Camera for Surveys (HST ACS) coronagraphic observations, and in one case dust may have already been detected. The observations of the planet Fomalhaut b can be explained as scattered light from dust produced by the collisional decay of an irregular satellite swarm around a .10 M_Earth planet. Such a swarm comprises about 5 lunar masses worth of irregular satellites. Finally, we briefly consider what happens if Fomalhaut b passes through Fomalhaut.s main debris ring on a coplanar orbit, which allows the circumplanetary swarm to be replenished through collisions with ring planetesimals. This scenario, in which the planet is at least of the order of an Earth mass, may be ruled out by the narrow structure of the debris ring.

 

 

Kocsis, B., Sesana, A., 2011, "Gas-driven massive black hole binaries: signatures in the nHz gravitational wave background," Monthly Notices of the Royal Astronomical Society, 57.

 

       Pulsar timing arrays (PTAs) measure nHz frequency gravitational waves (GWs) generated by orbiting massive black hole binaries (MBHBs) with periods between 0.1 and 10 yr. Previous studies on the nHz GW background assumed that the inspiral is purely driven by GWs. However, torques generated by a gaseous disc can shrink the binary much more efficiently than GW emission, reducing the number of binaries at these separations. We use simple disc models for the circumbinary gas and for the binary-disc interaction to follow the orbital decay of MBHBs through physically distinct regions of the disc, until GWs take over their evolution. We extract MBHB cosmological merger rates from the Millennium simulation, generate Monte Carlo realizations of a population of gas-driven binaries and calculate the corresponding GW amplitudes of the most luminous individual binaries and the stochastic GW background For steady state α-discs with α > 0.1, we find that the nHz GW background can be significantly modified. The number of resolvable binaries is however not changed by the presence of gas; we predict 1-10 individually resolvable sources to stand above the noise for a 1-50 ns timing precision. Gas-driven migration reduces predominantly the number of small total mass or unequal mass ratio binaries, which leads to the attenuation of the mean stochastic GW background, but increases the detection significance of individually resolvable binaries. The results are sensitive to the model of binary-disc interaction. The GW background is not attenuated significantly for time-dependent models of Ivanov, Papaloizou & Polnarev.

 

 

Kocsis, B., Tremaine, S., 2011, "Resonant relaxation and the warp of the stellar disc in the Galactic Centre," Monthly Notices of the Royal Astronomical Society, 3.

 

       Observations of the spatial distribution and kinematics of young stars in the Galactic Centre can be interpreted as showing that the stars occupy one, or possibly two, discs of radii .0.05-0.5 pc. The most prominent ("clockwise") disc exhibits a strong warp: the normals to the mean orbital planes in the inner and the outer third of the disc differ by .60°. Using an analytical model based on Laplace-Lagrange theory, we show that such warps arise naturally and inevitably through vector resonant relaxation between the disc and the surrounding old stellar cluster.

 

 

Konopliv, A.S., Asmar, S.W., Folkner, W.M., Karatekin, Ö, Nunes, D.C., Smrekar, S.E., Yoder, C.F., Zuber, M.T., 2011, "Mars high resolution gravity fields from MRO, Mars seasonal gravity, and other dynamical parameters," Icarus, 211, 401-428.

 

       With 2 years of tracking data collection from the MRO spacecraft, there is noticeable improvement in the high frequency portion of the spherical harmonic Mars gravity field. The new JPL Mars gravity fields, MRO110B and MRO110B2, show resolution near degree 90. Additional years of MGS and Mars Odyssey tracking data result in improvement for the seasonal J gravity changes which compares well to global circulation models and Odyssey neutron data and Mars rotation and precession (ψ˙=-7594±10mas/year). Once atmospheric dust is accounted for in the spacecraft solar pressure model, solutions for Mars solar tide are consistent between data sets and show slightly larger values (k₂ = 0.164 ± 0.009, after correction for atmospheric tide) compared to previous results, further constraining core models. An additional 4 years of Mars range data improves the Mars ephemeris, determines 21 asteroid masses and bounds solar mass loss (dGM_Sun/dt < 1.6 ×10^‑13 GM_Sun year^‑1).

 

 

Kostelecký., Tasson, J.D., 2011, "Matter-gravity couplings and Lorentz violation," Physical Review D, 83, 16013.

 

       The gravitational couplings of matter are studied in the presence of Lorentz and CPT violation. At leading order in the coefficients for Lorentz violation, the relativistic quantum Hamiltonian is derived from the gravitationally coupled minimal standard-model extension. For spin-independent effects, the nonrelativistic quantum Hamiltonian and the classical dynamics for test and source bodies are obtained. A systematic perturbative method is developed to treat small metric and coefficient fluctuations about a Lorentz-violating and Minkowski background. The post-Newtonian metric and the trajectory of a test body freely falling under gravity in the presence of Lorentz violation are established. An illustrative example is presented for a bumblebee model. The general methodology is used to identify observable signals of Lorentz and CPT violation in a variety of gravitational experiments and observations, including gravimeter measurements, laboratory and satellite tests of the weak equivalence principle, antimatter studies, solar-system observations, and investigations of the gravitational properties of light. Numerous sensitivities to coefficients for Lorentz violation can be achieved in existing or near-future experiments at the level of parts in 10³ down to parts in 10¹⁵. Certain coefficients are uniquely detectable in gravitational searches and remain unmeasured to date.

 

 

 

Lanza, A.F., Bonomo, A.S., Pagano, I., Leto, G., Messina, S., Cutispoto, G., Moutou, C., Aigrain, S., Alonso, R., Barge, P., Deleuil, M., Fridlund, M., Silva-Valio, A., Auvergne, M., Baglin, A., Collier Cameron, A., 2011, "Photospheric activity, rotation, and star-planet interaction of the planet-hosting star CoRoT-6," Astronomy and Astrophysics, 525, 14.

 

       Context. The CoRoT satellite has recently discovered a hot Jupiter that transits across the disc of a F9 main-sequence star called CoRoT-6 with a period of 8.886 days. 
Aims: We model the photospheric activity of the star and use the maps of the active regions to study stellar differential rotation and the star-planet interaction. 
Methods: We apply a maximum entropy spot model to fit the optical modulation as observed by CoRoT during a uninterrupted interval of ~ 140 days. Photospheric active regions are assumed to consist of spots and faculae in a fixed proportion with solar-like contrasts. 
Results: Individual active regions have lifetimes up to 30-40 days. Most of them form and decay within five active longitudes whose different migration rates are attributed to the stellar differential rotation for which a lower limit of ΔΩ/Ω = 0.12 ± 0.02 is obtained. Several active regions show a maximum of activity at a longitude lagging the subplanetary point by ~ 200° with the probability of a chance occurrence being smaller than 1 percent. 
Conclusions: Our spot modelling indicates that the photospheric activity of CoRoT-6 could be partially modulated by some kind of star-planet magnetic interaction, while an interaction related to tides is highly unlikely because of the weakness of the tidal force.

 

 

Lee, J.W., Lee, C.-U., Kim, S.-L., Kim, H.-I., Park, J.-H., 2011, "The Light and Period Variations of the Eclipsing Binary AA Ursae Majoris," Publications of the Astronomical Society of the Pacific, 123, 34-43.

 

       We present new multiband CCD photometry for AA UMa made on eight nights between 2009 January and March; the R light curves are the first ever compiled. Historical light curves, as well as ours, display partial eclipses and inverse O'Connell effects, with Max I fainter than Max II. Among possible spot models, a cool spot on either of the component stars and its variability with time permit good light-curve representations for the system. A total of 194 eclipse timings over 81 yr, including our five timings, were used for ephemeris computations. We found that the orbital period of the system has varied due to a periodic oscillation overlaid on an upward parabolic variation. The continuous period increase at a fractional rate of +1.3 ×10^-10 is consistent with that calculated from the Wilson & Devinney code and can be interpreted as a thermal mass transfer from the less massive to the more massive secondary star at a rate of 6.6 ×10^-8 M_ȯ yr^-1 . The periodic component is in satisfactory accord with a light-time effect due to an unseen companion with a period of 28.2 yr, a semiamplitude of 0.007 days, and a minimum mass of M₃ sin i₃ = 0.25 M_ȯ , but this period variation could also arise from magnetic activity.

 

 

Li, J.-Y., Kuchner, M.J., Allen, R.J., Sheppard, S.S., 2011, "Measuring the sizes, shapes, surface features and rotations of Solar System objects with interferometry," Icarus, 211, 1007-1021.

 

       We consider the application of interferometry to measuring the sizes and shapes of small bodies in the solar system that cannot be spatially resolved by today's single-dish telescopes. Assuming ellipsoidal shapes, our results indicate that interferometers can measure the size of an object to better than 15% uncertainty if the limb-darkening is unknown. Assuming a Minnaert scattering model, one can theoretically derive the limb-darkening parameters from simultaneous measurements of visibilities at several different projected baseline lengths to improve the size and shape determination to an accuracy of a few percent. With a 3-D shape model for the dwarf planet Haumea, we demonstrate that when photometric light curve, visibility light curve, and visibility phase center displacement are combined, the rotational period and sense of rotation can all be derived, and the rotational pole can be estimated. Because of its elongated shape and the dark red spot, the rotation of Haumea causes its optical photocenter to move in a loop on the sky, extending of ~80 μas without the dark red spot, and ~200 μas with it. Such movements are easily detectable by space-based astrometric interferometer designed e.g. for planet detection. As an example, we consider the possible contributions to the study of small bodies in the solar system by the Space Interferometry Mission. We show that such a mission could make substantial contributions in characterizing the fundamental physical properties of the brightest Kuiper Belt Objects and Centaurs as well as a large number of main belt asteroids. We compile a list of Kuiper Belt Objects and Centaurs that are potentially scientifically interesting and observable by such missions.

 

 

Libert, A.-S., Tsiganis, K., 2011, "Formation of '3D' multiplanet systems by dynamical disruption of multiple-resonance configurations," Monthly Notices of the Royal Astronomical Society, 54.

 

       Assuming that giant planets are formed in thin protoplanetary discs, a '3D' system - i.e. a planetary system composed of two (or more) planets, whose orbital planes have large values of mutual inclination - can form, provided that the mutual inclination is excited by some dynamical mechanism. Resonant interactions and close planetary encounters are thought to be the primary inclination-excitation mechanisms, resulting in a resonant and non-resonant system, respectively. If by the end of planet formation, the system is dynamically 'hot', then a phase of planet-planet scattering can be expected; however, this need not be the case in every system. Here we propose an alternative formation scenario, starting from a system composed of three giant planets in a nearly coplanar configuration. As was recently shown for the case of the Solar system, planetary migration in the gas disc (Type II migration) can force the planets to become trapped in a multiply resonant state (similar to the Laplace resonance in the Galilean satellites). We simulate this process, assuming different values for the planetary masses and mass ratios. We show that such a triple resonance generally becomes unstable as the resonance excites the eccentricities of all planets and planet-planet scattering sets in. One of the three planets is typically ejected from the system, leaving behind a dynamically 'hot' (but stable) two-planet configuration. The resulting two-planet systems typically have large values of semimajor axial ratios (α=a₁/a₂< 0.3), while the mutual inclination can be as high as 70°, with a median of .30°. These values are quite close to the ones recently obtained for the υ-Andromedae system. A small fraction of our two-planet systems (.5 per cent) ends up in the stability zone of the Kozai resonance. In a few cases, the triple resonance can remain stable for long times and a '3D' system can form by resonant excitation of the orbital inclinations; such a three-planet system could be stable if enough eccentricity damping is exerted on the planets. Finally, in the single-planet resulting systems, which are formed when two planets are ejected from the system, the inclination of the planet's orbital plane with respect to the initial invariant plane - presumably the plane perpendicular to the star's spin axis - can be as large as ~40°.

 

 

Lissauer, J.J., Fabrycky, D.C., Ford, E.B., Borucki, W.J., Fressin, F., Marcy, G.W., Orosz, J.A., Rowe, J.F., Torres, G., Welsh, W.F., Batalha, N.M., Bryson, S.T., Buchhave, L.A., Caldwell, D.A., Carter, J.A., Charbonneau, D., Christiansen, J.L., Cochran, W.D., Desert, J.-M., Dunham, E.W., Fanelli, M.N., Fortney, J.J., Gautier, T.N., III, Geary, J.C., Gilliland, R.L., Haas, M.R., Hall, J.R., Holman, M.J., Koch, D.G., Latham, D.W., Lopez, E., McCauliff, S., Miller, N., Morehead, R.C., Quintana, E.V., Ragozzine, D., Sasselov, D., Short, D.R., Steffen, J.H., 2011, "A closely packed system of low-mass, low-density planets transiting Kepler-11," Nature, 470, 53-58.

 

       When an extrasolar planet passes in front of (transits) its star, its radius can be measured from the decrease in starlight and its orbital period from the time between transits. Multiple planets transiting the same star reveal much more: period ratios determine stability and dynamics, mutual gravitational interactions reflect planet masses and orbital shapes, and the fraction of transiting planets observed as multiples has implications for the planarity of planetary systems. But few stars have more than one known transiting planet, and none has more than three. Here we report Kepler spacecraft observations of a single Sun-like star, which we call Kepler-11, that reveal six transiting planets, five with orbital periods between 10 and 47days and a sixth planet with a longer period. The five inner planets are among the smallest for which mass and size have both been measured, and these measurements imply substantial envelopes of light gases. The degree of coplanarity and proximity of the planetary orbits imply energy dissipation near the end of planet formation.

 

 

 

Maciejewski, G., Dimitrov, D., Neuhäer, R., Tetzlaff, N., Niedzielski, A., Raetz, S., Chen, W.P., Walter, F., Marka, C., Baar, S., KrejcováT., Budaj, J., Krushevska, V., Tachihara, K., Takahashi, H., Mugrauer, M., 2011, "Transit timing variation and activity in the WASP-10 planetary system," Monthly Notices of the Royal Astronomical Society, 411, 1204-1212.

 

       Transit timing analysis may be an effective method of discovering additional bodies in extrasolar systems that harbour transiting exoplanets. The deviations from the Keplerian motion, caused by mutual gravitational interactions between planets, are expected to generate transit timing variations of transiting exoplanets. In 2009, we collected nine light curves of eight transits of the exoplanet WASP-10b. Combining these data with those published, we have found that transit timing cannot be explained by a constant period but by a periodic variation. Simplified three-body models, which reproduce the observed variations of timing residuals, were identified by numerical simulations. We have found that the configuration with an additional planet with a mass of~0.1 M_Jand an orbital period of ~5.23 d, located close to the outer 5 : 3 mean motion resonance, is the most likely scenario. If the second planet is a transiter, the estimated flux drop will be .0.3 per cent and can be observed with a ground-based telescope. Moreover, we present evidence that the spots on the stellar surface and the rotation of the star affect the radial-velocity curve, giving rise to a spurious eccentricity of the orbit of the first planet. We argue that the orbit of WASP-10b is essentially circular. Using the gyrochronology method, the host star was found to be 270 ± 80 Myr old. This young age can explain the large radius reported for WASP-10b.

 

 

 

 

Malmberg, D., Davies, M.B., Heggie, D.C., 2011, "The effects of fly-bys on planetary systems," Monthly Notices of the Royal Astronomical Society, 411, 859-877.

 

       Most of the observed extrasolar planets are found on tight and often eccentric orbits. The high eccentricities are not easily explained by planet-formation models, which predict that planets should be on rather circular orbits. Here we explore whether fly-bys involving planetary systems with properties similar to those of the gas giants in the Solar system can produce planets with properties similar to the observed planets. Using numerical simulations, we show that fly-bys can cause the immediate ejection of planets, and sometimes also lead to the capture of one or more planets by the intruder. More common, however, is that fly-bys only perturb the orbits of planets, sometimes leaving the system in an unstable state. Over time-scales of a few million to several hundred million years after the fly-by, this perturbation can trigger planet-planet scatterings, leading to the ejection of one or more planets. For example, in the case of the four gas giants of the Solar system, the fraction of systems from which at least one planet is ejected more than doubles in 10⁸ yr after the fly-by. The remaining planets are often left on more eccentric orbits, similar to the eccentricities of the observed extrasolar planets. We combine our results of how fly-bys affect Solar-system-like planetary systems, with the rate at which encounters in young stellar clusters occur. For example, we measure the effects of fly-bys on the four gas giants in the Solar system. We find, that for such systems, between 5 and 15 per cent suffer ejections of planets in 10⁸ yr after fly-bys in typical open clusters. Thus, encounters in young stellar clusters can significantly alter the properties of any planets orbiting stars in clusters. As a large fraction of stars which populate the solar neighbourhood form in stellar clusters, encounters can significantly affect the properties of the observed extrasolar planets.

 

 

Mendoza, S., Hernandez, X., Hidalgo, J.C., Bernal, T., 2011, "A natural approach to extended Newtonian gravity: tests and predictions across astrophysical scales," Monthly Notices of the Royal Astronomical Society, 411, 226-234.

 

       In the pursuit of a general formulation for a modified gravitational theory at the non-relativistic level and as an alternative to the dark matter hypothesis, we construct a model valid over a wide variety of astrophysical scales. Through the inclusion of Milgrom's acceleration constant into a gravitational theory, we show that very general formulae can be constructed for the acceleration felt by a particle. Dimensional analysis shows that this inclusion naturally leads to the appearance of a mass-length scale in gravity, breaking its scale invariance. A particular form of the modified gravitational force is constructed and tested for consistency with observations over a wide range of astrophysical environments, from Solar system to extragalactic scales. We show that over any limited range of physical parameters, which define a specific class of astrophysical objects, the dispersion velocity of a system must be a power law of its mass and size. These powers appear linked together through a natural constraint relation of the theory. This yields a generalized gravitational equilibrium relation valid for all astrophysical systems. A general scheme for treating spherical symmetrical density distributions is presented, which in particular shows that the Fundamental Plane of elliptical galaxies, the Newtonian virial equilibrium, the Tully-Fisher and the Faber-Jackson relations, as well as the scalings observed in local dwarf spheroidal galaxies, are nothing but particular cases of that relation when applied to the appropriate mass-length scales. We discuss the implications of this approach for a modified theory of gravity and emphasize the advantages of working with the force, instead of altering Newton's second law of motion, in the formulation of a gravitational theory.

 

 

Meru, F., Bate, M.R., 2011, "Non-convergence of the critical cooling time-scale for fragmentation of self-gravitating discs," Monthly Notices of the Royal Astronomical Society, 411, L1-L5.

 

       We carry out a resolution study on the fragmentation boundary of self-gravitating discs. We perform three-dimensional Smoothed Particle Hydrodynamics simulations of discs to determine whether the critical value of the cooling time-scale in units of the orbital time-scale, b_crit, converges with increasing resolution. Using particle numbers ranging from 31 250 to 16 million (the highest resolution simulations to date) we do not find convergence. Instead, fragmentation occurs for longer cooling time-scales as the resolution is increased. These results suggest that at the very least, the critical value of the cooling time-scale is longer than previously thought. However, the absence of convergence also raises the question of whether or not a critical value exists. In light of these results, we caution against using cooling time-scale or gravitational stress arguments to deduce whether gravitational instability may or may not have been the formation mechanism for observed planetary systems.

 

 

Meschiari, S., Laughlin, G., Vogt, S.S., Butler, R.P., Rivera, E.J., Haghighipour, N., Jalowiczor, P., 2011, "The Lick-Carnegie Survey: Four New Exoplanet Candidates," The Astrophysical Journal, 727, 117.

 

       We present new precise HIRES radial velocity (RV) data sets of five nearby stars obtained at Keck Observatory. HD 31253, HD 218566, HD 177830, HD 99492, and HD 74156 are host stars of spectral classes F through K and show RV variations consistent with new or additional planetary companions in Keplerian motion. The orbital parameters of the candidate planets in the five planetary systems span minimum masses of Msin i = 27.43 M_Earth to 8.28 M_J, periods of 17.05-4696.95 days and eccentricities ranging from circular to extremely eccentric (e » 0.63). The fifth star, HD 74156, was known to have both a 52 day and a 2500 day planet, and was claimed to also harbor a third planet at 336 days, in apparent support of the "Packed Planetary System" hypothesis. Our greatly expanded data set for HD 74156 provides strong confirmation of both the 52 day and 2500 day planets, but strongly contradicts the existence of a 336 day planet, and offers no significant evidence for any other planets in the system.

 

 

Migaszewski, C., Goździewski, K., 2011, "The non-resonant, relativistic dynamics of circumbinary planets," Monthly Notices of the Royal Astronomical Society, 411, 565-583.

 

       We investigate a non-resonant, three-dimensional (spatial) model of a hierarchical system composed of a point-mass stellar (or substellar) binary and a low-mass companion (a circumbinary planet or a brown dwarf). We take into account the leading relativistic corrections to the Newtonian gravity. The secular model of the system relies on the expansion of the perturbing Hamiltonian in terms of the ratio of semi-major axes a, averaged over the mean anomalies. We found that a low-mass object in a distant orbit may excite a large eccentricity of the inner binary when the mutual inclination of the orbits is larger than about 60°. This is related to the strong instability caused by a phenomenon that acts similarly to the Lidov-Kozai resonance (LKR). The secular system may be strongly chaotic and its dynamics unpredictable over long-term time-scales. Our study shows that in the Jupiter- or brown-dwarf-mass regime of the low-mass companion, the restricted model does not properly describe the long-term dynamics in the vicinity of the LKR. The relativistic correction is significant for the parametric structure of a few families of stationary solutions in this problem, in particular for direct orbit configurations (with mutual inclination less than 90°). We found that the dynamics of hierarchical systems with small a~0.01 may be qualitatively different in the realms of Newtonian (classic) and relativistic models. This holds true even for relatively large masses of the secondaries.

 

 

Miyake, N., Sumi, T., Dong, S., Street, R., Mancini, L., Gould, A., Bennett, D.P., Tsapras, Y., Yee, J.C., Albrow, M.D., Bond, I.A., FouquéP., Browne, P., Han, C., Snodgrass, C., Finet, F., Furusawa, K., Harpsø., Allen, W., Hundertmark, M., Freeman, M., Suzuki, D., Abe, F., Botzler, C.S., Douchin, D., Fukui, A., Hayashi, F., Hearnshaw, J.B., Hosaka, S., Itow, Y., Kamiya, K., Kilmartin, P.M., Korpela, A., Lin, W., Ling, C.H., Makita, S., Masuda, K., Matsubara, Y., Muraki, Y., Nagayama, T., Nishimoto, K., Ohnishi, K., Perrott, Y.C., Rattenbury, N., Saito, T., Skuljan, L., Sullivan, D.J., Sweatman, W.L., Tristram, P.J., Wada, K., Yock, P.C.M., Collaboration, M., Bolt, G., Bos, M., Christie, G.W., DePoy, D.L., Drummond, J., Gal-Yam, A., Gaudi, B.S., Gorbikov, E., Higgins, D., Hwang, K.-H., Janczak, J., Kaspi, S., Lee, C.-U., Koo, J.-R., Koz?owski, S., Lee, Y., Mallia, F., Maury, A., Maoz, D., McCormick, J., Monard, L.A.G., Moorhouse, D., Muñ J.A., Natusch, T., Ofek, E.O., Pogge, R.W., Polishook, D., Santallo, R., Shporer, A., Spector, O., Thornley, G., Collaboration, F., Allan, A., Bramich, D.M., Horne, K., Kains, N., Steele, I., Collaboration, R., Bozza, V., Burgdorf, M.J., Calchi Novati, S., Dominik, M., Dreizler, S., Glitrup, M., Hessman, F.V., Hinse, T.C., Jøsen, U.G., Liebig, C., et al., 2011, "A Sub-Saturn Mass Planet, MOA-2009-BLG-319Lb," The Astrophysical Journal, 728, 120.

 

       We report the gravitational microlensing discovery of a sub-Saturn mass planet, MOA-2009-BLG-319Lb, orbiting a K- or M-dwarf star in the inner Galactic disk or Galactic bulge. The high-cadence observations of the MOA-II survey discovered this microlensing event and enabled its identification as a high-magnification event approximately 24 hr prior to peak magnification. As a result, the planetary signal at the peak of this light curve was observed by 20 different telescopes, which is the largest number of telescopes to contribute to a planetary discovery to date. The microlensing model for this event indicates a planet-star mass ratio of q = (3.95 ± 0.02) ×10^-4 and a separation of d = 0.97537 ± 0.00007 in units of the Einstein radius. A Bayesian analysis based on the measured Einstein radius crossing time, t _E, and angular Einstein radius, θ_E, along with a standard Galactic model indicates a host star mass of M _L = 0.38^+0.34 _-0.18 M _sun and a planet mass of M _p = 50⁺⁴⁴ _-24 M _⊕, which is half the mass of Saturn. This analysis also yields a planet-star three-dimensional separation of a = 2.4^+1.2 _-0.6 AU and a distance to the planetary system of D _L = 6.1^+1.1 _-1.2 kpc. This separation is ~2 times the distance of the snow line, a separation similar to most of the other planets discovered by microlensing.

 

 

 

Molaro, P., CenturióM., 2011, "Ceres' sunlight atlas," Astronomy and Astrophysics, 525, 74.

 

       Context. Astronomical research dealing with accurate radial velocity measurements need reliable astronomical standards to calibrate the spectrographs and to assess possible systematics. Stellar radial velocity standards offer a reference at the level of a few hundred m s^-1 and are not adequate for most present needs.

 

Aims: We aim to show that sunlight reflected by asteroids is a fairly accessible way to record a high-resolution solar spectrum from the whole disk, which can therefore be used as a radial velocity standard and can improve the uncertainties of solar line positions.

 

Methods: We used solar light reflected by the asteroid Ceres observed with HARPS to measure solar lines' wavelengths.

 

Results: We provide a new solar atlas with 491 line wavelengths in the range 540-690 nm and 222 lines in the range 400-410 nm obtained from reflected solar spectrum of Ceres. These measurements are consistent with those of Allende Prieto & Garcia Lopez (1998b) based on FTS solar atlases but with a factor 3 higher precision.

 

Conclusions: This atlas provides a benchmark for wavelength calibration to check radial velocity accuracy down to 44 m s^-1 locally and a few m s^-1 globally. The asteroid-based technique could provide a new way to track radial velocity shifts with solar activity cycle, as well as to derive convective shifts suitable for comparison with theoretical atmospheric models. It could also be used to study radial velocity deviations in spectrographs such as those recently detected in HIRES and UVES. Dedicated HARPS observations of other asteroids could improve present results substantially and these investigations have been solicited. Full Table 2 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/525/A74.

 

 

Morais, M.H.M., Correia, A.C.M., 2011, "Stellar wobble caused by a nearby binary system: eccentric and inclined orbits," Astronomy and Astrophysics, 525, 152.

 

       Most extrasolar planets currently known were discovered by means of an indirect method that measures the stellar wobble caused by the planet. We previously studied a triple system composed of a star and a nearby binary on circular coplanar orbits. We showed that although the effect of the binary on the star can be differentiated from the stellar wobble caused by a planet, because of observational limitations the two effects may often remain indistinguishable. Here, we develop a model that applies to eccentric and inclined orbits. We show that the binary's effect is more likely to be mistaken by planet(s) in the case of coplanar motion observed equator-on. Moreover, when the orbits are eccentric, the magnitude of the binary's effect may be larger than in the circular case. Additionally, an eccentric binary can mimic two planets with orbital periods in the ratio 2/1. However, when the star's orbit around the binary's center of mass has a high eccentricity and a reasonably well-constrained period, it should be easier to distinguish the binary's effect from a planet.

 

 

Mordasini, C., Mayor, M., Udry, S., Lovis, C., Séansan, D., Benz, W., Bertaux, J.-L., Bouchy, F., Lo Curto, G., Moutou, C., Naef, D., Pepe, F., Queloz, D., Santos, N.C., 2011, "The HARPS search for southern extra-solar planets. XXIV. Companions to HD 85390, HD 90156, and HD 103197: a Neptune analog and two intermediate-mass planets," Astronomy and Astrophysics, 526, 111.

 

       We report the detection of three new extrasolar planets orbiting the solar type stars HD 85390, HD 90156 and HD 103197 with the HARPS spectrograph mounted on the ESO 3.6-m telescope at La Silla observatory. HD 85390 has a planetary companion with a projected intermediate mass (42.0 M_⊕) on a 788-day orbit (a = 1.52 AU) with an eccentricity of 0.41, for which there is no analog in the solar system. A drift in the data indicates the presence of another companion on a long-period orbit, which is however not covered by our measurements. HD 90156 is orbited by a warm Neptune analog with a minimum mass of 17.98 M_⊕ (1.05 MM_neptune, a period of 49.8 days (a = 0.25 AU), and an eccentricity of 0.31. HD 103197 has an intermediate-mass planet on a circular orbit (P = 47.8 d, M sin i = 31.2 M_⊕). We discuss the formation of planets of intermediate mass (30-100 M_⊕), which should be rare inside a few AU according to core accretion formation models.

 

 

Moudden, Y., Forbes, J.M., 2011, "Simulated planetary wave-tide interactions in the atmosphere of Mars," Journal of Geophysical Research (Planets), 116, 01004.

 

       This study is a first attempt to simulate the nonlinear interactions between planetary waves and tides in the atmosphere of Mars and to examine the consequences of the secondary waves that result from these interactions. Recent analysis of aerobraking densities show clear signatures of secondary waves produced by the modulation of tides by planetary waves. The vertically propagating secondary waves serve to modulate longitudinal density structures (due to nonmigrating tides) at planetary wave periods, even in the local absence of planetary waves. In this parametric study, using a general circulation model of Mars, we determine the most important waves produced by these interactions and quantify their induced variability at aerobraking altitudes.

 

 

Mü T.G., ?urech, J., Hasegawa, S., Abe, M., Kawakami, K., Kasuga, T., Kinoshita, D., Kuroda, D., Urakawa, S., Okumura, S., Sarugaku, Y., Miyasaka, S., Takagi, Y., Weissman, P.R., Choi, Y.-J., Larson, S., Yanagisawa, K., Nagayama, S., 2011, "Thermo-physical properties of 162173 (1999 JU3), a potential flyby and rendezvous target for interplanetary missions," Astronomy and Astrophysics, 525, 145.

 

       Context. Near-Earth asteroid 162173 (1999 JU3) is a potential flyby and rendezvous target for interplanetary missions because of its easy-to-reach orbit. The physical and thermal properties of the asteroid are relevant for establishing the scientific mission goals and also important in the context of near-Earth object studies in general.

 

Aims: Our goal was to derive key physical parameters such as shape, spin-vector, size, geometric albedo, and surface properties of 162173 (1999 JU3).

 

Methods: With three sets of published thermal observations (ground-based N-band, Akari IRC, Spitzer IRS), we applied a thermophysical model to derive the radiometric properties of the asteroid. The calculations were performed for the full range of possible shape and spin-vector solutions derived from the available sample of visual lightcurve observations. 
Results: The near-Earth asteroid 162173 (1999 JU3) has an effective diameter of 0.87 ± 0.03 km and a geometric albedo of 0.070 ± 0.006. The χ²-test reveals a strong preference for a retrograde sense of rotation with a spin-axis orientation of λ_ecl = 73°, β_ecl = -62° and P_sid = 7.63 ± 0.01 h. The most likely thermal inertia ranges between 200 and 600 J m^-2 s^-0.5 K^-1, about a factor of 2 lower than the value for 25143 Itokawa. This indicates that the surface lies somewhere between a thick-dust regolith and a rock/boulder/cm-sized, gravel-dominated surface like that of 25143 Itokawa. Our analysis represents the first time that shape and spin-vector information has been derived from a combined data set of visual lightcurves (reflected light) and mid-infrared photometry and spectroscopy (thermal emission).

 

 

Na, X.S., Wang, N., Yuan, J.P., Liu, Z.Y., Esamdin, A., Pan, J., Xu, R.X., 2011, "Hurst parameter analysis of radio pulsar timing residuals," Monthly Notices of the Royal Astronomical Society, 163.

 

       We analyse the timing residuals for 50 pulsars observed using the Nanshan 25-m radio telescope at Urumqi Observatory by determining the Hurst parameter for each data set using the rescaled range method. These pulsars have been observed over a time span of 5-8 yr and have been selected to have timing residuals that resemble white noise rather than smooth curves. The results are compared with those for shuffled residual series. Despite the noise-like appearance, some timing residual series showed Hurst parameters that deviated significantly from the shuffled series. We conclude that Hurst parameter analysis is capable of detecting long-term memory in timing residuals.

 

 

Nakada, M., 2011, "Earth's rotational variations due to rapid surface flows at both boundaries of the outer core," Geophysical Journal International, 184, 235-246.

 

       Rapid geomagnetic fluctuations with periods less than a couple of years, so called geomagnetic jerks, are coincident with sharp changes in rate of change of Earth's length of day (LOD) and phase of the Chandler wobble. Here I examine the rotational variations in response to sudden changes of toroidal core surface flows for geomagnetic jerks, assuming rigid rotation of the outer core and core surface flows at both boundaries (CMB and ICB) with the magnitude of .3 km yr^-1. I take into account the gravitational torque acting on the inner core associated with convective processes in the mantle and the electromagnetic (EM) coupling for a model with conductivity of the core of 5 ×10+⁵ S m^-1 and a 200 m conducting layer of 5 ×10⁵ S m^-1 at the bottom of the mantle. The present study indicates that rapid accelerations of the flow at the CMB can produce LOD change consistent with observed LOD derivative with ~0.1 ms yr^-1, but do not produce much for the polar motion. On the other hand, rapid accelerations of the flow at the ICB insignificantly affect the LOD change, but can produce polar motion signals that might affect the Chandler wobble if we adopt the EM coupling for a model with the flows of ~3 km yr^-1 and root-mean-square value of 4~5 mT for the radial magnetic field at the ICB.

 

 

Namouni, F., 2011, "On dynamical friction in a gaseous medium with a boundary," Astrophysics and Space Science, 331, 575-595.

 

       Dynamical friction arises from the interaction of a perturber and the gravitational wake it excites in the ambient medium. We study the effects of the presence of a boundary on dynamical friction by studying analytically the interaction of perturber with uniform rectilinear motion in a uniform homogeneous medium with a reflecting planar boundary. Wake reflection at a medium's boundary may occur at the edges of truncated disks perturbed by planetary or stellar companions as well as in numerical simulations of planet-disk interaction with no-outflow boundary conditions. In this paper, we show that the presence of the boundary modifies the behaviour of dynamical friction significantly. We find that perturbers are invariably pushed away from the boundary and reach a terminal subsonic velocity near Mach 0.37 regardless of initial velocity. Dynamical friction may even be reversed for Mach numbers less than 0.37 thereby accelerating instead of decelerating the perturber. Perturbers moving parallel to the boundary feel additional friction orthogonal to the direction of motion that is much stronger than the standard friction along the direction of motion. These results indicate that the common use of the standard Chandrasekhar formula as a short hand estimate of dynamical friction may be inadequate as observed in various numerical simulations.

 

 

Nayakshin, S., 2011, "Rotation of the Solar system planets and the origin of the Moon in the context of the tidal downsizing hypothesis," Monthly Notices of the Royal Astronomical Society, 410, L1-L5.

 

       It has been proposed recently that the first step in the formation of both rocky and gas giant planets is dust sedimentation into a solid core inside a gas clump (giant planet embryo). The clumps are then assumed to migrate closer to the star where their metal poor envelopes are sheared away by the tidal forces or by an irradiation-driven mass loss. We consider the implications of this hypothesis for natal rotation rates of both terrestrial and gas giant planets. It is found that both types of planets may rotate near their breakup angular frequencies at birth. The direction of the spin should coincide with that of the parent disc and the star, except in cases of embryos that had close interactions or mergers with other embryos in the past. Furthermore, the large repository of specific angular momentum at birth also allows formation of close binary rocky planets inside the same embryos. We compare these predictions with rotation rates of planets in the Solar system and also question whether the Earth-Moon pair could have been formed within the same giant planet embryo.

 

 

 

Nutzman, P., Gilliland, R.L., McCullough, P.R., Charbonneau, D., Christensen-Dalsgaard, J., Kjeldsen, H., Nelan, E.P., Brown, T.M., Holman, M.J., 2011, "Precise Estimates of the Physical Parameters for the Exoplanet System HD 17156 Enabled by Hubble Space Telescope Fine Guidance Sensor Transit and Asteroseismic Observations," The Astrophysical Journal, 726, 3.

 

       We present observations of three distinct transits of HD 17156b obtained with the Fine Guidance Sensors on board the Hubble Space Telescope. We analyzed both the transit photometry and previously published radial velocities to find the planet-star radius ratio R_p /R _sstarf = 0.07454 ± 0.00035, inclination i = 86.49^+0.24 _-0.20 deg, and scaled semimajor axis a/R _sstarf = 23.19^+0.32 _-0.27. This last value translates directly to a mean stellar density determination ρ_sstarf = 0.522^+0.021 _-0.018 g cm^-3. Analysis of asteroseismology observations by the companion paper of Gilliland et al. provides a consistent but significantly refined measurement of ρ_sstarf = 0.5308 ± 0.0040. We compare stellar isochrones to this density estimate and find M _sstarf = 1.275 ± 0.018 M _sun and a stellar age of 3.37^+0.20 _-0.47 Gyr. Using this estimate of M _sstarf and incorporating the density constraint from asteroseismology, we model both the photometry and published radial velocities to estimate the planet radius R_p= 1.0870 ± 0.0066 R_J and the stellar radius R _sstarf = 1.5007 ± 0.0076 R _sun. The planet radius is larger than that found in previous studies and consistent with theoretical models of a solar-composition gas giant of the same mass and equilibrium temperature. For the three transits, we determine the times of mid-transit to a precision of 6.2 s, 7.6 s, and 6.9 s, and the transit times for HD 17156 do not show any significant departures from a constant period. The joint analysis of transit photometry and asteroseismology presages similar studies that will be enabled by the NASA Kepler Mission.

 

Olgin, J.G., Smith-Konter, B.R., Pappalardo, R.T., 2011, "Limits of Enceladus's ice shell thickness from tidally driven tiger stripe shear failure," Geophysical Research Letters, 38, 02201.

 

       Enceladus's south polar thermal anomaly and water-rich plumes suggest the existence of a subsurface ocean, which is overlain by an ice shell of uncertain thickness. Our objective is to constrain Enceladus's ice shell thickness, through assessment of tidally driven Coulomb failure of Enceladus's tiger stripe faults. We find that thin to moderate ice shell thicknesses (<40 km) support shear failure along the tiger stripes, assuming low ice coefficients of friction (0.1.0.3) and shallow fault depths (<3 km). These results are marginally consistent with the minimum ice shell thickness which can permit convection within Enceladus's ice shell. A plausible scenario is one in which the heat loss and tectonic style of Enceladus has changed through time, with convection initiating in a thick ice shell, and tiger stripe activity commencing as the ice shell thinned.

 

 

Pahlevan, K., Stevenson, D.J., Eiler, J.M., 2011, "Chemical fractionation in the silicate vapor atmosphere of the Earth," Earth and Planetary Science Letters, 301, 433-443.

 

       Despite its importance to questions of lunar origin, the chemical composition of the Moon is not precisely known. In recent years, however, the isotopic composition of lunar samples has been determined to high precision and found to be indistinguishable from the terrestrial mantle despite widespread isotopic heterogeneity in the Solar System. In the context of the giant-impact hypothesis, this level of isotopic homogeneity can evolve if the proto-lunar disk and post-impact Earth undergo turbulent mixing into a single uniform reservoir while the system is extensively molten and partially vaporized. In the absence of liquid.vapor separation, such a model leads to the lunar inheritance of the chemical composition of the terrestrial magma ocean. Hence, the turbulent mixing model raises the question of how chemical differences arose between the silicate Earth and Moon. Here we explore the consequences of liquid.vapor separation in one of the settings relevant to the lunar composition: the silicate vapor atmosphere of the post-giant-impact Earth. We use a model atmosphere to quantify the extent to which rainout can generate chemical differences by enriching the upper atmosphere in the vapor, and show that plausible parameters can generate the postulated enhancement in the FeO/MgO ratio of the silicate Moon relative to the Earth's mantle. Moreover, we show that liquid.vapor separation also generates measurable mass-dependent isotopic offsets between the silicate Earth and Moon and that precise silicon isotope measurements can be used to constrain the degree of chemical fractionation during this earliest period of lunar history. An approach of this kind has the potential to resolve long-standing questions on the lunar chemical composition.

 

 

Pasetto, S., Grebel, E.K., Berczik, P., Chiosi, C., Spurzem, R., 2011, "Orbital evolution of the Carina dwarf galaxy and self-consistent determination of star formation history," Astronomy and Astrophysics, 525, 99.

 

       We present a new study of the evolution of the Carina dwarf galaxy that includes a simultaneous derivation of its orbit and star formation history. The structure of the galaxy is constrained through orbital parameters derived from the observed distance, proper motions, radial velocity, and star formation history. The different orbits admitted by the large proper motion errors are investigated in relation to the tidal force exerted by an external potential representing the Milky Way. Our analysis is performed with the aid of fully consistent N-body simulations that are able to follow the dynamics and the stellar evolution of the dwarf system in order to determine the star formation history of Carina self-consistently. We also find a star formation history characterized by several bursts, partially matching the observational expectation. We find also compatible results between dynamical projected quantities and the observational constraints. The possibility of a past interaction between Carina and the Magellanic Clouds is also separately considered and deemed unlikely. Appendices are only available in electronic form at <A href="http://www.aanda.org">http://www.aanda.org</A>

 

 

Perets, H.B., 2011, "Binary Planetesimals and Their Role in Planet Formation," The Astrophysical Journal, 727, L3.

 

       One of the main evolutionary stages of planet formation is the dynamical evolution of planetesimal disks. These disks are thought to evolve through gravitational encounters and physical collisions between single planetesimals. In recent years, many binary planetesimals (BPs) have been observed in the solar system, indicating that the binarity of planetesimals is high. However, current studies of planetesimal disk formation and evolution do not account for the role of binaries. Here, we point out that gravitational encounters of BPs can have an important role in the evolution of planetesimal disks. BPs catalyze close encounters between planetesimals and can strongly enhance their collision rate. Binaries may also serve as an additional heating source of the planetesimal disk, through the exchange of the binaries gravitational potential energy into the kinetic energy of planetesimals in the disk.

 

 

 

Perryman, M.A.C., Schulze-Hartung, T., 2011, "The barycentric motion of exoplanet host stars. Tests of solar spin-orbit coupling," Astronomy and Astrophysics, 525, 65.

 

       Context. Empirical evidence suggests a tantalising but unproven link between various indicators of solar activity and the barycentric motion of the Sun. The latter is exemplified by transitions between regular and more disordered motion modulated by the motions of the giant planets, and rare periods of retrograde motion with negative orbital angular momentum. An examination of the barycentric motion of exoplanet host stars, and their stellar activity cycles, has the potential of proving or disproving the Sun's motion as an underlying factor in the complex patterns of short- and long-term solar variability indices, by establishing whether such correlations exist in other planetary systems. In either case, these studies may lead to further insight into the nature of the solar dynamo.

 

Aims: Some 40 multiple exoplanet systems are now known, all with reasonably accurate orbital elements. The forms and dynamical functions of the barycentric motion of their host stars are examined. These results can be compared with long-term activity indicators of exoplanet host stars, as they become available, to examine whether the correlations claimed for the Sun also exist in other systems.

 

Methods: Published orbital elements of multiple exoplanetary systems are used to examine their host star barycentric motions. For each system, we determine analytically the orbital angular momentum of the host star, and its rate of change.

 

Results: A variety of complex patterns of barycentric motions of exoplanet host stars is demonstrated, depending on the number, masses and orbits of the planets. Each of the behavioural types proposed to correlate with solar activity are also evident in exoplanet host stars: repetitive patterns influenced by massive multiple planets, epochs of rapid change in orbital angular momentum, and intervals of negative orbital angular momentum.

 

Conclusions: The study provides the basis for independent investigations of the widely-studied but unproven suggestion that the Sun's motion is somehow linked to various indicators of solar activity. We show that, because of the nature of their barycentric motions, the host stars HD 168443 and HD 74156 offer particularly powerful tests of this hypothesis.

 

 

Pierrehumbert, R.T., 2011, "A Palette of Climates for Gliese 581g," The Astrophysical Journal, 726, L8.

 

       We consider a range of possible climates for the habitable-zone planet candidate, Gliese 581g, contingent on a plausible set of hypothetical atmospheres and assuming the planet to be tide locked. The two most habitable states we find are (1) a nearly airless Super-Europa with thin ice at the substellar point and (2) an "Eyeball Earth" which is mostly frozen but supports a substantial stable pool of open water centered on the substellar point. We discuss the prospects for observational determination of what kind of climate 581g actually supports.

 

 

Pires Dos Santos, P.M., Giuliatti Winter, S.M., Sfair, R., 2011, "Gravitational effects of Nix and Hydra in the external region of the Pluto-Charon system," Monthly Notices of the Royal Astronomical Society, 410, 273-279.

 

       Two new companions to the Pluto-Charon binary system have been detected in 2005 by Weaver et al. These small satellites, named Nix and Hydra, are located beyond Charon's orbit. Although they are small when compared to Charon, their gravitational perturbations can decrease the stability of the external region (beyond Charon's orbit). The dynamical structure of this external region is analysed by numerically simulating a sample of particles under the gravitational effects of Pluto, Charon, Nix and Hydra. As expected the effects of Nix and Hydra decrease the external stable region. Agglomerates of particles can survive even after 10<SUP>5</SUP> orbital periods of the binary in some regions, such as coorbital to Nix and Hydra and between their orbits. We also analysed the effects of hypothetical satellites on the orbital evolution of Nix and Hydra in order to constrain an upper limit size. Some hypothetical satellites can be coorbital to Nix or Hydra without provoking any significant gravitational effects on them.

 

 

Qin, L., Nittler, L.R., Alexander, C.M.O.D., Wang, J., Stadermann, F.J., Carlson, R.W., 2011, "Extreme 54Cr-rich nano-oxides in the CI chondrite Orgueil . Implication for a late supernova injection into the solar system," Geochimica et Cosmochimica Acta, 75, 629-644.

 

       Systematic variations in 54Cr/52Cr ratios between meteorite classes (Qin et al., 2010a; Trinquier et al., 2007) point to large scale spatial and/or temporal isotopic heterogeneity in the solar protoplanetary disk. Two explanations for these variations have been proposed, with important implications for the formation of the Solar System: heterogeneous seeding of the disk with dust from a supernova, or energetic-particle irradiation of dust in the disk. The key to differentiating between them is identification of the carrier(s) of the 54Cr anomalies. Here we report the results of our recent NanoSIMS imaging search for the 54Cr-rich carrier in the acid-resistant residue of the CI chondrite Orgueil. A total of 10 regions with extreme 54Cr-excesses ({\delta}54Cr values up to 1500 %) were found. Comparison between SEM, Auger and NanoSIMS analyses showed that these 54Cr-rich regions are associated with one or more sub-micron (typically less than 200 nm) Cr oxide grains, most likely spinels. Because the size of the NanoSIMS primary O- ion beam is larger than the typical grain size on the sample mount, the measured anomalies are lower limits, and we estimate that the actual 54Cr enrichments in three grains are at least 11 times Solar and in one of these may be as high as 50 times Solar. Such compositions strongly favor a Type II supernova origin. The variability in bulk 54Cr/52Cr between meteorite classes argues for a heterogeneous distribution of the 54Cr carrier in the solar protoplanetary disk following a late supernova injection event. Such a scenario is also supported by the O-isotopic distribution and variable abundances in different planetary materials of other presolar oxide and silicate grains from supernovae.

 

 

Rafikov, R.R., 2011, "Constraint on the Giant Planet Production by Core Accretion," The Astrophysical Journal, 727, 86.

 

       The issue of giant planet formation by core accretion (CA) far from the central star is rather controversial because the growth of a massive solid core necessary for triggering the gas runaway can take longer than the lifetime of the protoplanetary disk. In this work, we assess the range of separations at which CA may operate by (1) allowing for an arbitrary (physically meaningful) rate of planetesimal accretion by the core and (2) properly taking into account the dependence of the critical mass for the gas runaway on the planetesimal accretion luminosity. This self-consistent approach distinguishes our work from similar studies in which only a specific planetesimal accretion regime was explored and/or the critical core mass was fixed at some arbitrary level. We demonstrate that the largest separation at which the gas runaway can occur within 3 Myr corresponds to the surface density of solids in the disk >~0.1 g cm^.2 and is 40-50 AU in the minimum mass solar nebula. This limiting separation is achieved when the planetesimal accretion proceeds at the fastest possible rate, even though the high associated accretion luminosity increases the critical core mass, delaying the onset of gas runaway. Our constraints are independent of the mass of the central star and vary only weakly with the core density and its atmospheric opacity. We also discuss various factors that can strengthen or weaken our limits on the operation of CA.

 

 

Redmer, R., Mattsson, T.R., Nettelmann, N., French, M., 2011, "The phase diagram of water and the magnetic fields of Uranus and Neptune," Icarus, 211, 798-803.

 

       The interior of giant planets can give valuable information on formation and evolution processes of planetary systems. However, the interior and evolution of Uranus and Neptune is still largely unknown. In this paper, we compare water-rich three-layer structure models of these planets with predictions of shell structures derived from magnetic field models. Uranus and Neptune have unusual non-dipolar magnetic fields contrary to that of the Earth. Extensive three-dimensional simulations of Stanley and Bloxham (Stanley, S., Bloxham, J. [2004]. Nature 428, 151.153) have indicated that such a magnetic field is generated in a rather thin shell of at most 0.3 planetary radii located below the H/He rich outer envelope and a conducting core that is fluid but stably stratified. Interior models rely on equation of state data for the planetary materials which have usually considerable uncertainties in the high-pressure domain. We present interior models for Uranus and Neptune that are based on ab initio equation of state data for hydrogen, helium, and water as the representative of all heavier elements or ices. Based on a detailed high-pressure phase diagram of water we can specify the region where superionic water should occur in the inner envelope. This superionic region correlates well with the location of the stably-stratified region as found in the dynamo models. Hence we suggest a significant impact of the phase diagram of water on the generation of the magnetic fields in Uranus and Neptune.

 

 

Reich, E.S., 2011, "Astronomy: Beyond the stars," Nature, 470, 24-26.

 

       Launched in 2009 to seek out worlds beyond the Solar System, the Kepler mission is exceeding expectations. Is it closing in on another Earth?

 

 

Riaz, B., Martí E.L., 2011, "Large-amplitude photometric variability of the candidate protoplanet TMR-1C," Astronomy and Astrophysics, 525, 10.

 

       Context. TMR-1C is a candidate protoplanet that lies at a separation of about 10. (~1000 AU) from the Class I protobinary TMR-1 (IRAS 04361+2547) located in the Taurus molecular cloud. A narrow filament-like structure was observed in the discovery HST/NICMOS images, extending southeast from the central proto-binary system towards TMR-1C, suggesting a morphology in which the candidate protoplanet may have been ejected from the TMR-1 system. Follow-up low-resolution spectroscopy, however, could not confirm if this object is a protoplanet or a low-luminosity background star.

 

Aims: We present two epochs of near-infrared photometric observations obtained at the CFHT of TMR-1C. The time span of ~7 years between the two sets of observations provides an opportunity to (a) check for any photometric variability similar to that observed among young stellar objects, which would indicate the youth of this source, and to (b) determine the proper motion.

 

Results: TMR-1C displays large photometric variability between 1 and 2 mag in both the H- and K_s-bands. From our 2002 observations, we find a (H-K_s) color of 0.3 mag, which is much bluer than the value of 1.3 mag reported by T98 from HST observations. Also, we observe brightening in both the H- and K_s-bands when the colors are bluer; i.e., the object gets redder as it becomes fainter. We have explored the possible origins for the observed variability, and find extinction due to the presence of circumstellar material to be the most likely scenario. The observed large-amplitude photometric variations and the possible presence of a circumstellar disk are strong arguments against this object being an old background star.

 

 

Riggio, A., Papitto, A., Burderi, L., di Salvo, T., Bachetti, M., Iaria, R., D'AìA., Menna, M.T., 2011, "Timing of the accreting millisecond pulsar IGR J17511-3057," Astronomy and Astrophysics, 526, 95.

 

       Context. Timing analysis of accretion-powered millisecond pulsars (AMPs) is a powerful tool for probing the physics of compact objects. The recently discovered IGR J17511-3057 was the twelfth discovered of the 13 AMPs known. The Rossi XTE satellite provided an extensive coverage of the 25 days-long observation of the source outburst.

 

Aims: Our goal is to investigate the complex interaction between the neutron star magnetic field and the accretion disk by determining the angular momentum exchange between them. The presence of a millisecond coherent flux modulation allows us to investigate this interaction from the study of pulse arrival times. To separate the neutron star proper spin frequency variations from other effects, a precise set of orbital ephemeris is mandatory.

 

Methods: Using timing techniques, we analysed the pulse phase delays by fitting differential corrections to the orbital parameters. To remove the effects of pulse phase fluctuations, we applied the timing technique that had been already successfully applied to the case of another AMP, XTE J1807-294.

 

Results: We report a precise set of orbital ephemeris. We demonstrate that the companion star is a main-sequence star. We find pulse phase delay fluctuations on the first harmonic with a characteristic amplitude of about 0.05, similar to those also observed for the AMP XTE J1814-338. For the second time, an AMP shows a third harmonic detected during the entire outburst. The first harmonic phase delays exhibit a puzzling behaviour, while the second harmonic phase delays clearly spin-up. The third harmonic also shows a spin-up, although not highly significant (3s c.l.). The presence of a fourth harmonic is also reported. If we assume that the second harmonic is a good tracer of the spin frequency of the neutron star, we infer a mean spin frequency derivative for this source of 1.65(18) ×10 10^-13 Hz s^-1.

 

Conclusions: To interpret the pulse phase delays of the four harmonics, we apply the disk threading model, but obtain different and incompatible dot{M} estimates for each harmonic. In particular, the phase delays of the first harmonic are heavily affected by phase noise, and consequently, on the basis of these data, it is not possible to derive a reliable estimate of dot{M}. The second harmonic gives a dot{M} consistent with the flux assuming that the source is at a distance of 6.3 kpc. The third harmonic gives a lower dot{M} value, with respect to the first and second harmonic, and this would reduce the distance estimate to 3.6 kpc.

 

 

Rojo, P., Margot, J.L., 2011, "Mass and Density of the B-type Asteroid (702) Alauda," The Astrophysical Journal, 727, 69.

 

       Observations with the adaptive optics system on the Very Large Telescope reveal that the outer main belt asteroid (702) Alauda has a small satellite with primary to secondary diameter ratio of ~56. The secondary revolves around the primary in 4.9143 ± 0.007 days at a distance of 1227 ± 24 km, yielding a total system mass of (6.057 ± 0.36) ×10¹⁸ kg. Combined with an IRAS size measurement, our data yield a bulk density of 1570 ± 500 kg m^.3 for this B-type asteroid.

 

 

Rosen, R., McLaughlin, M.A., Thompson, S.E., 2011, "A Non-radial Oscillation Model for Pulsar State Switching," The Astrophysical Journal, 728, L19.

 

       Pulsars are unique astrophysical laboratories because of their clock-like timing precision, providing new ways to test general relativity and detect gravitational waves. One impediment to high-precision pulsar timing experiments is timing noise. Recently, Lyne et al. showed that the timing noise in a number of pulsars is due to quasi-periodic fluctuations in the pulsars' spin-down rates and that some of the pulsars have associated changes in pulse profile shapes. Here we show that a non-radial oscillation model based on asteroseismological theory can explain these quasi-periodic fluctuations. Application of this model to neutron stars will increase our knowledge of neutron star emission and neutron star interiors and may improve pulsar timing precision.

 

 

Rosenburg, M.A., Aharonson, O., Head, J.W., Kreslavsky, M.A., Mazarico, E., Neumann, G.A., Smith, D.E., Torrence, M.H., Zuber, M.T., 2011, "Global surface slopes and roughness of the Moon from the Lunar Orbiter Laser Altimeter," Journal of Geophysical Research (Planets), 116, 02001.

 

       The acquisition of new global elevation data from the Lunar Orbiter Laser Altimeter, carried on the Lunar Reconnaissance Orbiter, permits quantification of the surface roughness properties of the Moon at unprecedented scales and resolution. We map lunar surface roughness using a range of parameters: median absolute slope, both directional (along-track) and bidirectional (in two dimensions); median differential slope; and Hurst exponent, over baselines ranging from ~17 m to ~2.7 km. We find that the lunar highlands and the mare plains show vastly different roughness properties, with subtler variations within mare and highlands. Most of the surface exhibits fractal-like behavior, with a single or two different Hurst exponents over the given baseline range; when a transition exists, it typically occurs near the 1 km baseline, indicating a significant characteristic spatial scale for competing surface processes. The Hurst exponent is high within the lunar highlands, with a median value of 0.95, and lower in the maria (with a median value of 0.76). The median differential slope is a powerful tool for discriminating between roughness units and is useful in characterizing, among other things, the ejecta surrounding large basins, particularly Orientale, as well as the ray systems surrounding young, Copernican-age craters. In addition, it allows a quantitative exploration on mare surfaces of the evolution of surface roughness with age.

 

 

Rubie, D.C., Frost, D.J., Mann, U., Asahara, Y., Nimmo, F., Tsuno, K., Kegler, P., Holzheid, A., Palme, H., 2011, "Heterogeneous accretion, composition and core.mantle differentiation of the Earth," Earth and Planetary Science Letters, 301, 31-42.

 

       A model of core formation is presented that involves the Earth accreting heterogeneously through a series of impacts with smaller differentiated bodies. Each collision results in the impactor's metallic core reacting with a magma ocean before merging with the Earth's proto-core. The bulk compositions of accreting planetesimals are represented by average solar system abundances of non-volatile elements (i.e. CI-chondritic), with 22% enhancement of refractory elements and oxygen contents that are defined mainly by the Fe metal/FeO silicate ratio. Based on an anhydrous bulk chemistry, the compositions of coexisting core-forming metallic liquid and peridotitic silicate liquid are calculated by mass balance using experimentally-determined metal/silicate partition coefficients for the elements Fe, Si, O, Ni, Co, W, Nb, V, Ta and Cr. Oxygen fugacity is fixed by the partitioning of Fe between metal and silicate and depends on temperature, pressure and the oxygen content of the starting composition. Model parameters are determined by fitting the calculated mantle composition to the primitive mantle composition using least squares minimization. Models that involve homogeneous accretion or single-stage core formation do not provide acceptable fits. In the most successful models, involving 24 impacting bodies, the initial 60.70% (by mass) of the Earth accretes from highly-reduced material with the final 30.40% of accreted mass being more oxidised, which is consistent with results of dynamical accretion simulations. In order to obtain satisfactory fits for Ni, Co and W, it is required that the larger (and later) impactor cores fail to equilibrate completely before merging with the Earth's proto-core, as proposed previously on the basis of Hf-W isotopic studies. Estimated equilibration conditions may be consistent with magma oceans extending to the core.mantle boundary, thus making core formation extremely efficient. The model enables the compositional evolution of the Earth's mantle and core to be predicted throughout the course of accretion. The results are consistent with the late accretion of the Earth's water inventory, possibly with a late veneer after core formation was complete. Finally, the core is predicted to contain ~ 5 wt.% Ni, ~ 8 wt.% Si, ~ 2 wt.% S and ~ 0.5 wt.% O.

 

 

Sáhez, P., Scheeres, D.J., 2011, "Simulating Asteroid Rubble Piles with A Self-gravitating Soft-sphere Distinct Element Method Model," The Astrophysical Journal, 727, 120.

 

       This paper applies a soft-sphere distinct element method Granular Dynamics code to simulate asteroid regolith and rubble piles. Applications to regolith studies in low gravity are also studied. Then an algorithm to calculate self-gravity is derived and incorporated for full-scale simulations of rubble-pile asteroids using Granular Dynamics techniques. To test its validity, the algorithm's results are compared with the exact direct calculation of the gravitational forces. Further avenues to improve the performance of the algorithm are also discussed.

 

 

Sandell, G., Weintraub, D.A., Hamidouche, M., 2011, "A Submillimeter Mapping Survey of Herbig AeBe Stars," The Astrophysical Journal, 727, 26.

 

       We have acquired submillimeter observations of 33 fields containing 37 Herbig Ae/Be (HAEBE) stars or potential HAEBE stars, including SCUBA maps of all but two of these stars. Nine target stars show extended dust emission. The other 18 are unresolved, suggesting that the dust envelopes or disks around these stars are less than a few arcseconds in angular size. In several cases, we find that the strongest submillimeter emission originates from younger, heavily embedded sources rather than from the HAEBE star, which means that previous models must be viewed with caution. These new data, in combination with far-infrared flux measurements available in the literature, yield spectral energy distributions (SEDs) from far-infrared to millimeter wavelengths for all the observed objects. Isothermal fits to these SEDs demonstrate excellent fits, in most cases, to the flux densities longward of 100 mm. We find that a smaller proportion of B-type stars than A- and F-type stars are surrounded by circumstellar disks, suggesting that disks around B stars dissipate on shorter timescales than those around later spectral types. Our models also reveal that the mass of the circumstellar material and the value of b are correlated, with low masses corresponding to low values of b. Since low values of b imply large grain sizes, our results suggest that a large fraction of the mass in low- b sources is locked up in very large grains. Several of the isolated HAEBE stars have disks with very flat submillimeter SEDs. These disks may be on the verge of forming planetary systems.

 

 

Santos, N.C., Mayor, M., Bonfils, X., Dumusque, X., Bouchy, F., Figueira, P., Lovis, C., Melo, C., Pepe, F., Queloz, D., Séansan, D., Sousa, S.G., Udry, S., 2011, "The HARPS search for southern extrasolar planets. XXV. Results from the metal-poor sample," Astronomy and Astrophysics, 526, 112.

 

       Searching for extrasolar planets around stars of different metallicity may provide strong constraints to the models of planet formation and evolution. In this paper we present the overall results of a HARPS (a high-precision spectrograph mostly dedicated to deriving precise radial velocities) program to search for planets orbiting a sample of 104 metal-poor stars (selected [Fe/H] below -0.5). Radial velocity time series of each star are presented and searched for signals using several statistical diagnostics. Stars with detected signals are presented, including 3 attributed to the presence of previously announced giant planets orbiting the stars HD 171028, HD 181720, and HD 190984. Several binary stars and at least one case of a coherent signal caused by activity-related phenomena are presented. One very promising new, possible giant planet orbiting the star HD 107094 is discussed, and the results are analyzed in light of the metallicity-giant planet correlation. We conclude that the frequency of giant planets orbiting metal-poor stars may be higher than previously thought, probably reflecting the higher precision of the HARPS survey. In the metallicity domain of our sample, we also find evidence that the frequency of planets is a steeply rising function of the stellar metal content, as found for higher metallicity stars. Based on observations collected at the La Silla Parana Observatory, ESO (Chile) with the HARPS spectrograph at the 3.6-m telescope (ESO runs ID 72.C-0488, 082.C-0212, and 085.C-0063).Full Tables 1 and 3 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/526/A112

 

 

Savransky, D., Cady, E., Kasdin, N.J., 2011, "Parameter Distributions of Keplerian Orbits," The Astrophysical Journal, 728, 66.

 

       Starting with just the assumption of uniformly distributed orbital orientations, we derive expressions for the distributions of the Keplerian orbital elements as functions of arbitrary distributions of eccentricity and semimajor axis. We present methods for finding the probability density functions of the true anomaly, eccentric anomaly, orbital radius, and other parameters used in describing direct planetary observations. We also demonstrate the independence of the distribution of phase angle, which is highly significant in the study of direct searches, and present examples validating the derived expressions.

 

 

Schlichting, H.E., Sari, R.e., 2011, "Runaway Growth During Planet Formation: Explaining the Size Distribution of Large Kuiper Belt Objects," The Astrophysical Journal, 728, 68.

 

       Runaway growth is an important stage in planet formation during which large protoplanets form, while most of the initial mass remains in small planetesimals. The amount of mass converted into large protoplanets and their resulting size distribution are not well understood. Here, we use analytic work, that we confirm by coagulation simulations, to describe runaway growth and the corresponding evolution of the velocity dispersion. We find that runaway growth proceeds as follows. Initially, all the mass resides in small planetesimals, with mass surface density σ, and large protoplanets start to form by accreting small planetesimals. This growth continues until growth by merging large protoplanets becomes comparable to growth by planetesimal accretion. This condition sets in when Σ/σ ~ α^3/4 ~ 10^-3, where Σ is the mass surface density in protoplanets in a given logarithmic mass interval and α is the ratio of the size of a body to its Hill radius. From then on, protoplanetary growth and the evolution of the velocity dispersion become self-similar and Σ remains roughly constant, since an increase in Σ by accretion of small planetesimals is balanced by a decrease due to merging with large protoplanets. We show that this growth leads to a protoplanet size distribution given by N(>R) vprop R ^-3, where N(>R) is the number of objects with radii greater than R (i.e., a differential power-law index of 4). Since only the largest bodies grow significantly during runaway growth, Σ and thereby the size distribution are preserved. We apply our results to the Kuiper Belt, which is a relic of runaway growth where planet formation never proceeded to completion. Our results successfully match the observed Kuiper Belt size distribution, they illuminate the physical processes that shaped it and explain the total mass that is present in large Kuiper Belt objects (KBOs) today. This work suggests that the current mass in large KBOs is primordial and that it has not been significantly depleted. We also predict a maximum mass ratio for Kuiper Belt binaries that formed by dynamical processes of α^-1/4 ~ 10, which explains the observed clustering in binary companion sizes that is seen in the cold classical belt. Finally, our results also apply to growth in debris disks, as long as frequent planetesimal-planetesimal collisions are not important during the growth.

 

 

Shevchenko, I.I., 2011, "The Kepler map in the three-body problem," New Astronomy, 16, 94-99.

 

       The Kepler map was derived by Petrosky (1986) and Chirikov and Vecheslavov (1986) as a tool for description of the long-term chaotic orbital behaviour of the comets in nearly parabolic motion. It is a two-dimensional area-preserving map, describing the motion of a comet in terms of energy and time. Its second equation is based on Kepler.s third law, hence the title of the map. Since 1980s the Kepler map has become paradigmatic in a number of applications in celestial mechanics and atomic physics. It represents an important kind of general separatrix maps. Petrosky and Broucke (1988) used refined methods of mathematical physics to derive analytical expressions for its single parameter. These methods became available only in the second half of the 20th century, and it may seem that the map is inherently a very modern mathematical tool. With the help of the Jacobi integral I show that the Kepler map, including analytical formulae for its parameter, can be derived by quite elementary methods. The prehistory and applications of the Kepler map are considered and discussed.

 

 

Sicardy, B., Bolt, G., Broughton, J., Dobosz, T., Gault, D., Kerr, S., Bérd, F., Frappa, E., Lecacheux, J., Peyrot, A., Teng-Chuen-Yu, J.-P., Beisker, W., Boissel, Y., Buckley, D., Colas, F., de Witt, C., Doressoundiram, A., Roques, F., Widemann, T., Gruhn, C., Batista, V., Biggs, J., Dieters, S., Greenhill, J., Groom, R., Herald, D., Lade, B., Mathers, S., Assafin, M., Camargo, J.I.B., Vieira-Martins, R., Andrei, A.H., da Silva Neto, D.N., Braga-Ribas, F., Behrend, R., 2011, "Constraints on Charon's Orbital Elements from the Double Stellar Occultation of 2008 June 22," The Astronomical Journal, 141, 67.

 

       Pluto and its main satellite, Charon, occulted the same star on 2008 June 22. This event was observed from Australia and La Réion Island, providing the east and north Charon Plutocentric offset in the sky plane (J2000): X= + 12,070.5 ± 4 km (+ 546.2 ± 0.2 mas), Y= + 4,576.3 ± 24 km (+ 207.1 ± 1.1 mas) at 19:20:33.82 UT on Earth, corresponding to JD 2454640.129964 at Pluto. This yields Charon's true longitude L= 153.483 ± 0fdg071 in the satellite orbital plane (counted from the ascending node on J2000 mean equator) and orbital radius r= 19,564 ± 14 km at that time. We compare this position to that predicted by (1) the orbital solution of Tholen & Buie (the "TB97" solution), (2) the PLU017 Charon ephemeris, and (3) the solution of Tholen et al. (the "T08" solution). We conclude that (1) our result rules out solution TB97, (2) our position agrees with PLU017, with differences of ΔL= + 0.073 ± 0fdg071 in longitude, and Δr= + 0.6 ± 14 km in radius, and (3) while the difference with the T08 ephemeris amounts to only ΔL= 0.033 ± 0.071° in longitude, it exhibits a significant radial discrepancy of Δr= 61.3 ± 14 km. We discuss this difference in terms of a possible image scale relative error of 3.35 ×10^-3in the 2002-2003 Hubble Space Telescope images upon which the T08 solution is mostly based. Rescaling the T08 Charon semi-major axis, a = 19, 570.45 km, to the TB97 value, a = 19636 km, all other orbital elements remaining the same ("T08/TB97" solution), we reconcile our position with the re-scaled solution by better than 12 km (or 0.55 mas) for Charon's position in its orbital plane, thus making T08/TB97 our preferred solution.

 

Simpson, E.K., Faedi, F., Barros, S.C.C., Brown, D.J.A., Collier Cameron, A., Hebb, L., Pollacco, D., Smalley, B., Todd, I., Butters, O.W., Héard, G., McCormac, J., Miller, G.R.M., Santerne, A., Street, R.A., Skillen, I., Triaud, A.H.M.J., Anderson, D.R., Bento, J., Boisse, I., Bouchy, F., Enoch, B., Haswell, C.A., Hellier, C., Holmes, S., Horne, K., Keenan, F.P., Lister, T.A., Maxted, P.F.L., Moulds, V., Moutou, C., Norton, A.J., Parley, N., Pepe, F., Queloz, D., Segransan, D., Smith, A.M.S., Stempels, H.C., Udry, S., Watson, C.A., West, R.G., Wheatley, P.J., 2011, "WASP-37b: A 1.8 M J Exoplanet Transiting a Metal-poor Star," The Astronomical Journal, 141, 8.

 

       We report on the discovery of WASP-37b, a transiting hot Jupiter orbiting an m _v = 12.7 G2-type dwarf, with a period of 3.577469 ± 0.000011 d, transit epoch T ₀ = 2455338.6188 ± 0.0006 (HJD; dates throughout the paper are given in Coordinated Universal Time (UTC)), and a transit duration 0.1304^+0.0018 _-0.0017 d. The planetary companion has a mass M _p = 1.80 ± 0.17 M _J and radius R _p = 1.16^+0.07 _-0.06 R _J, yielding a mean density of 1.15^+0.12 _-0.15 ρ_J. From a spectral analysis, we find that the host star has M _sstarf = 0.925 ± 0.120 M _sun, R _sstarf = 1.003 ± 0.053 R _sun, T _eff = 5800 ± 150 K, and [Fe/H] = -0.40 ± 0.12. WASP-37 is therefore one of the lowest metallicity stars to host a transiting planet.

 

Singh, J., Begha, J.M., 2011, "Stability of equilibrium points in the generalized perturbed restricted three-body problem," Astrophysics and Space Science, 331, 511-519.

 

       This paper studies the existence and stability of equilibrium points under the influence of small perturbations in the Coriolis and the centrifugal forces, together with the non-sphericity of the primaries. The problem is generalized in the sense that the bigger and smaller primaries are respectively triaxial and oblate spheroidal bodies. It is found that the locations of equilibrium points are affected by the non-sphericity of the bodies and the change in the centrifugal force. It is also seen that the triangular points are stable for 0< μ< μ _c and unstable for μ_c≤μ <1/2, where μ _c is the critical mass parameter depending on the above perturbations, triaxiality and oblateness. It is further observed that collinear points remain unstable

 

 

Tanikawa, A., Umemura, M., 2011, "Successive Merger of Multiple Massive Black Holes in a Primordial Galaxy," The Astrophysical Journal, 728, L31.

 

       Using highly accurate N-body simulations, we explore the evolution of multiple massive black holes (hereafter MBHs) in a primordial galaxy that is composed of stars and MBHs. The evolution is pursed with a fourth-order Hermite scheme, where not only three-body interaction of MBHs but also dynamical friction by stars are incorporated. Initially, 10 MBHs with equal masses of 10⁷ M _sun are set in a host galaxy with 10¹¹ M _sun. It is found that 4-6 MBHs merge successively within 1 Gyr, emitting gravitational wave radiation. The key process for the successive merger of MBHs is the dynamical friction by field stars, which enhances three-body interactions of MBHs when they enter the central regions of the galaxy. The heaviest MBH always composes a close binary at the galactic center, which shrinks owing to the angular momentum transfer by the third MBH and eventually merges. The angular momentum transfer by the third MBH is due to the sling-shot mechanism. We find that the secular Kozai mechanism does not work for a binary to merge if we include the relativistic pericenter shift. The simulations show that a multiple MBH system can produce a heavier MBH at the galactic center purely through N-body process. This merger path can be of great significance for the growth of MBHs in a primordial galaxy. The merger of multiple MBHs may be a potential source of gravitational waves for the Laser Interferometer Space Antenna and pulsar timing.

 

 

Taris, F., Souchay, J., Andrei, A.H., Bernard, M., Salabert, M., Bouquillon, S., Anton, S., Lambert, S.B., Gontier, A.-M., Barache, C., 2011, "Astrophotometric variability of CFHT-LS Deep 2 QSOs," Astronomy and Astrophysics, 526, 25.

 

       Context. The current conventional realization of the ICRS (International Celestial Reference System) is, in the radio wavelength, the International Celestial Reference Frame 2 (ICRF2). The individual positions of the defining sources have been found to have accuracies better than 1 milliarcsecond (mas). In 2012, the European astrometric satellite Gaia will be launched. This mission will provide an astrometric catalog of an estimated number of 500 000 QSOs. The uncertainty in the coordinates is anticipated to be 200 microarcsecond (mas) for the magnitude = 20. If this were achieved, the ICRF and the Gaia related reference frame could be related with a mas accuracy.

 

Aims: The goal of this work is both to measure the photometric variability of a set of quasars in a given field, and search wether this variability can be related to an astrometric instability characterized by a motion of the quasar photocenter. If this correlation existed for some given QSO, then it would be inadequate to materialize the Gaia extragalactic reference frame at the level of confidence required, i.e. the sub-milliarcsecond one. This should be an important result in the scope of the Gaia mission.

 

Methods: We use QSO CCD images obtained over 4.5 years with the Canada France Hawaïelescope (CFHT) in the framework of the CFHT-Legacy Survey (CFHT-LS). The pictures were analysed with both the SExtractor software and customised codes to perform a photometric calibration together with an astrometric one. A total of 41 QSOs in the Deep 2 field were analysed. Magnitude variations during more than 50 months are given at three different bandwiths G, R, and I. Among the set above, 5 quasars were chosen to test the ties between the postion of their centroid and their magnitude variations. For one of these 5 QSOs, the proximity of a neighbouring star allows the comparison between the PSFs.

 

Results: We clearly show significant photometric variations reaching sometimes more than one magnitude, for a good proportion of the 41 quasars in our sample. We show that these variations often occur within a few months, and that the correlation between the photometric curves in the three bands, G, R and I is obvious. As a second important result, we show that with a reasonably high probability, photometric variations for one quasar in our sample are accompagnied by substantial modification of its PSF. This paper is dedicated to the memory of Anne-Marie Gontier (1966-2010). A.-M. Gontier was an expert in the field of Earth rotation, reference systems and the modeling, analysis, and processing of VLBI observations for astrometric and geodetic applications.Figures 4-14 are only available in electronic form at http://www.aanda.org

 

 

Team, T.G.P., Gendt, G., Altamimi, Z., Dach, R., Sö, W., Springer, T., 2011, "GGSP: Realisation and maintenance of the Galileo Terrestrial Reference Frame," Advances in Space Research, 47, 174-185.

 

       The realisation and maintenance of a Galileo Terrestrial Reference Frame (GTRF) is the main function of the Galileo Geodetic Service Provider (GGSP). The GTRF shall be compatible with the latest International Terrestrial Reference Frame (ITRF) within a precision level of 3 cm (2 sigma). The connection to the ITRF is realized and validated by stations of the International GNSS Service (IGS) and by geodetic local ties to stations equipped with other geodetic techniques. It is demonstrated that this GTRF can be maintained by including the Galileo Signal-in-Space data, once Galileo reaches its operational stage.The GGSP will also provide additional products, such as Earth Rotation Parameters, satellites orbits, clock corrections for satellites and stations, which will be offered to the Galileo user community to have most precise access to the GTRF and will be used to monitor the accuracy of the corresponding Galileo Mission Segment.The GGSP was built up in time, and for a final demonstration the full system was operated for an interval of 6 months. During that time also microwave data from the two active GIOVE satellites were used.The GGSP Consortium followed the most up to date IGS standards of weekly processing during seven monthly campaigns (November 2006 to June 2008) and a continuous processing from September 2008 to February 2009 delivering several versions of the GTRF. The latest GTRF solution (GTRF09v01) has an RMS position difference with respect to the ITRF2005 computed over the 71 common stations of 1.1 and 2.9 mm in the horizontal and vertical components, respectively. The RMS velocity differences are 0.3 and 0.6 mm/y, respectively. The GGSP GPS satellite orbits and clock corrections agree with the IGS Final products at a level of 5.11 mm and 0.02.0.03 ns, respectively.The quality of the GIOVE orbits is at a level of 20.30 cm. The Hydrogen-Maser on board of GIOVE-B is nearly one order of magnitude better than the GPS satellite clocks.

 

 

Tingley, B., Bonomo, A.S., Deeg, H.J., 2011, "Using Stellar Densities to Evaluate Transiting Exoplanetary Candidates," The Astrophysical Journal, 726, 112.

 

       One of the persistent complications in searches for transiting exoplanets is the low percentage of the detected candidates that ultimately prove to be planets, which significantly increases the load on the telescopes used for the follow-up observations to confirm or reject candidates. Several attempts have been made at creating techniques that can pare down candidate lists without the need of additional observations. Some of these techniques involve a detailed analysis of light curve characteristics; others estimate the stellar density or some proxy thereof. In this paper, we extend upon this second approach, exploring the use of independently calculated stellar densities to identify the most promising transiting exoplanet candidates. We use a set of CoRoT candidates and the set of known transiting exoplanets to examine the potential of this approach. In particular, we note the possibilities inherent in the high-precision photometry from space missions, which can detect stellar asteroseismic pulsations from which accurate stellar densities can be extracted without additional observations.

 

 

Tinney, C.G., Butler, R.P., Jones, H.R.A., Wittenmyer, R.A., O'Toole, S., Bailey, J., Carter, B.D., 2011, "The Anglo-Australian Planet Search. XX. A Solitary Ice-giant Planet Orbiting HD 102365," The Astrophysical Journal, 727, 103.

 

       We present 12 years of precision Doppler data for the very nearby G3 star HD 102365, which reveals the presence of a Neptune-like planet with a 16.0 M_Earth minimum mass in a 122.1 day orbit. Very few "Super Earth" planets have been discovered to date in orbits this large and those that have been found reside in multiple systems of between three and six planets. HD 102365 b, in contrast, appears to orbit its star in splendid isolation. Analysis of the residuals to our Keplerian fit for HD 102365 b indicates that there are no other planets with minimum mass above 0.3 M _Jup orbiting within 5 AU and no other "Super Earths" more massive than 10 M_Earth orbiting at periods shorter than 50 days. At periods of less than 20 days these limits drop to as low as 6 M_Earth. There are now 32 exoplanets known with minimum mass below 20 M_Earth, and interestingly the period distributions of these low-mass planets seem to be similar whether they orbit M-, K-, or G-type dwarfs.

 

Titov, O.A., 2011, "Estimation of the acceleration of the solar-system barycenter relative to a system of reference quasars," Astronomy Reports, 55, 91-95.

 

       It is shown that geodetic VLBI observations can be used to estimate the external acceleration of the barycenter of the solar system. This relies on the fact that, in special relativity, the acceleration of the motion of a coordinate origin relative to reference points leads to a drift in the secular aberration, manifest as systematic proper motions of the reference points in the direction of the acceleration vector. The VLBI time-delay equation is modified such that the acceleration vector appears in explicit form. Formulas for a new form of the fundamental VLBI equation and its partial derivative with respect to the acceleration are presented.

 

 

Torres, G., Fressin, F., Batalha, N.M., Borucki, W.J., Brown, T.M., Bryson, S.T., Buchhave, L.A., Charbonneau, D., Ciardi, D.R., Dunham, E.W., Fabrycky, D.C., Ford, E.B., Gautier, T.N., III, Gilliland, R.L., Holman, M.J., Howell, S.B., Isaacson, H., Jenkins, J.M., Koch, D.G., Latham, D.W., Lissauer, J.J., Marcy, G.W., Monet, D.G., Prsa, A., Quinn, S.N., Ragozzine, D., Rowe, J.F., Sasselov, D.D., Steffen, J.H., Welsh, W.F., 2011, "Modeling Kepler Transit Light Curves as False Positives: Rejection of Blend Scenarios for Kepler-9, and Validation of Kepler-9 d, A Super-earth-size Planet in a Multiple System," The Astrophysical Journal, 727, 24.

 

       Light curves from the Kepler Mission contain valuable information on the nature of the phenomena producing the transit-like signals. To assist in exploring the possibility that they are due to an astrophysical false positive, we describe a procedure (BLENDER) to model the photometry in terms of a "blend" rather than a planet orbiting a star. A blend may consist of a background or foreground eclipsing binary (or star-planet pair) whose eclipses are attenuated by the light of the candidate and possibly other stars within the photometric aperture. We apply BLENDER to the case of Kepler-9 (KIC 3323887), a target harboring two previously confirmed Saturn-size planets (Kepler-9 b and Kepler-9 c) showing transit timing variations, and an additional shallower signal with a 1.59 day period suggesting the presence of a super-Earth-size planet. Using BLENDER together with constraints from other follow-up observations we are able to rule out all blends for the two deeper signals and provide independent validation of their planetary nature. For the shallower signal, we rule out a large fraction of the false positives that might mimic the transits. The false alarm rate for remaining blends depends in part (and inversely) on the unknown frequency of small-size planets. Based on several realistic estimates of this frequency, we conclude with very high confidence that this small signal is due to a super-Earth-size planet (Kepler-9 d) in a multiple system, rather than a false positive. The radius is determined to be 1.64^+0.19_.0.14 R_Earth, and current spectroscopic observations are as yet insufficient to establish its mass.

 

 

Townsend, L.J., Coe, M.J., Corbet, R.H.D., McBride, V.A., Hill, A.B., Bird, A.J., Schurch, M.P.E., Haberl, F., Sturm, R., Pathak, D., van Soelen, B., Bartlett, E.S., Drave, S.P., Udalski, A., 2011, "The orbital solution and spectral classification of the high-mass X-ray binary IGR J01054-7253 in the Small Magellanic Cloud," Monthly Notices of the Royal Astronomical Society, 410, 1813-1824.

 

       We present X-ray and optical data on the Be/X-ray binary (BeXRB) pulsar IGR J 01054−7253= SXP11.5 in the Small Magellanic Cloud (SMC). Rossi X-ray Timing Explorer (RXTE) observations of this source in a large X-ray outburst reveal an 11.483 ± 0.002 s pulse period and show both the accretion-driven spin-up of the neutron star and the motion of the neutron star around the companion through Doppler shifting of the spin period. Model fits to these data suggest an orbital period of 36.3 ± 0.4 d and  of (4.7 ± 0.3) ×10⁻¹⁰  seconds s⁻¹. We present an orbital solution for this system, making it one of the best-described BeXRB systems in the SMC. The observed pulse period, spin-up and X-ray luminosity of SXP11.5 in this outburst are found to agree with the predictions of neutron star accretion theory. Timing analysis of the long-term optical light curve reveals a periodicity of 36.70 ± 0.03 d, in agreement with the orbital period found from the model fit to the X-ray data. Using blue-end spectroscopic observations we determine the spectral type of the counterpart to be O9.5-B0 IV.V. This luminosity class is supported by the observed V-band magnitude. Using optical and near-infrared photometry and spectroscopy, we study the circumstellar environment of the counterpart in the months after the X-ray outburst.

 

 

Ulamec, S., Kucherenko, V., Biele, J., Bogatchev, A., Makurin, A., Matrossov, S., 2011, "Hopper concepts for small body landers," Advances in Space Research, 47, 428-439.

 

       The investigation of small bodies, comets and asteroids, can contribute substantially to our understanding of the formation and history of the Solar System. In situ observations by landers play an important role in this field.Due to the low gravity of comets and asteroids, mobility of surface elements can be achieved by hopping devices, providing relatively low delta-v.The first such hopper was part of the Soviet Phobos 2 Mission in the 1980s.The current paper presents the results of a study for a small (.10 kg) hopper device, optimized for a mission to a relatively small asteroid. The hopper may, e.g. be considered as part of the Japanese Hayabusa 2 mission, to be launched in the 2014/15 timeframe.Concepts for the actuation of the hopper, dynamics and mechanical aspects are discussed in further detail.

 

 

Veras, D., Ford, E.B., Payne, M.J., 2011, "Quantifying the Challenges of Detecting Unseen Planetary Companions with Transit Timing Variations," The Astrophysical Journal, 727, 74.

 

       Both ground- and space-based transit observatories are poised to significantly increase the number of known transiting planets and the number of precisely measured transit times. The variation in a planet's transit times may be used to infer the presence of additional planets. Deducing the masses and orbital parameters of such planets from transit time variations (TTVs) alone is a rich and increasingly relevant dynamical problem. In this work, we evaluate the extent of the degeneracies in this process, systematically explore the dependence of TTV signals on several parameters, and provide phase space plots that could aid observers in planning future observations. Our explorations are focused on a likely-to-be prevalent situation: a known transiting short-period Neptune- or Jupiter-sized planet and a suspected external low-mass perturber on a nearly coplanar orbit. Through ~10⁷ N-body simulations, we demonstrate how TTV signal amplitudes may vary by orders of magnitude due to slight variations in any one orbital parameter (10^.3 AU in a semimajor axis, 0.005 in eccentricity, or a few degrees in orbital angles), and quantify the number of consecutive transit observations necessary in order to obtain a reasonable opportunity of characterizing the unseen planet (>~50 observations). Planets in or near period commensurabilities of the form p:q, where p <= 20 and q <= 3, produce distinct TTV signatures, regardless of whether the planets are actually locked in a mean motion resonance. We distinguish these systems from the secular systems in our explorations. Additionally, we find that computing the autocorrelation function of a TTV signal can provide a useful diagnostic for identifying possible orbits for additional planets and suggest that this method could aid integration of TTV signals in future studies of particular exosystems.

 

 

 

Walsh, K.J., Morbidelli, A., 2011, "The effect of an early planetesimal-driven migration of the giant planets on terrestrial planet formation," Astronomy and Astrophysics, 526, 126.

 

       The migration of the giant planets due to the scattering of planetesimals causes powerful resonances to move through the asteroid belt and the terrestrial planet region. Exactly when and how the giant planets migrated is not well known. In this paper we present results of an investigation of the formation of the terrestrial planets during and after the migration of the giant planets. The latter is assumed to have occurred immediately after the dissipation of the nebular disk - i.e. "early" with respect to the timing of the late heavy bombardment (LHB). The presumed cause of our modeled early migration of the giant planets is angular mometum transfer between the planets and scattered planetesimals. Our model forms the terrestrial planets from a disk of material which stretchs from 0.3-4.0 AU, evenly split in mass between planetesimals and planetary embryos. Jupiter and Saturn are initially at 5.4 and 8.7 AU respectively, on orbits with eccentricities comparable to the current ones, and migrate to 5.2 and 9.4 AU with an e-folding time of 5 Myr. Unfortunately, the terrestrial planets formed in the simulations are not good analogs for the current solar system, with Mars typically being much too massive. Moreover, the final distribution of the planetesimals remaining in the asteroid belt is inconsistent with the observed distribution of asteroids. This argues that, even if giant planet migration had occurred early, the real evolution of the giant planets would have to have been of the "jumping-Jupiter" type, i.e. the increase in orbital separation between Jupiter and Saturn had to be dominated by encounters between Jupiter and a third, Neptune-mass planet. This result was already demonstrated for late migrations occuring at the LHB time by previous work, and this paper shows those conclusions hold for early migration as well.

 

 

Wen, D.-H., Chen, W., 2011, "GEOPHYSICS, ASTRONOMY AND ASTROPHYSICS Properties of hyperon stars rotating at Keplerian frequency," Chinese Physics B, 20, 9701.

 

       The structure and properties of a Keplerian rotating hyperon star with an equation of state (EOS) investigated using the relativistic σ-ω-ρ model are examined by employing an accurate numerical scheme. It is shown that there is a clear rotating effect on the structure and properties, and that hyperon star matter cannot support a star with a mass larger than 1.9 M_odot, even a star rotating at the fastest allowed frequency. The constraints of the two known fastest rotating frequencies (716 Hz and 1122 Hz) on the mass and radius of a hyperon star are also explored. Furthermore, our results indicate that the imprint of the rapid rotation of a hyperon star on the moment of inertia is clear; the backward equatorial redshift, the forward equatorial redshift and the polar redshift can be distinguished clearly, the forward equatorial redshift is always negative; and its figuration is far from a spherical symmetric shape.

 

 

Wilner, D.J., Andrews, S.M., Hughes, A.M., 2011, "Millimeter Imaging of the b Pictoris Debris Disk: Evidence for a Planetesimal Belt," The Astrophysical Journal, 727, L42.

 

       We present observations at 1.3 mm wavelength of the β Pictoris debris disk with beam size 4.3. ×2.6. (83 ×50 AU) from the Submillimeter Array. The emission shows two peaks separated by ~7'' along the disk plane, which we interpret as a highly inclined dust ring or belt. A simple model constrains the belt center to 94 ± 8 AU, close to the prominent break in slope of the optical scattered light. We identify this region as the location of the main reservoir of dust-producing planetesimals in the disk.

 

 

Winn, J.N., Howard, A.W., Johnson, J.A., Marcy, G.W., Isaacson, H., Shporer, A., Bakos, G.Á, Hartman, J.D., Holman, M.J., Albrecht, S., Crepp, J.R., Morton, T.D., 2011, "Orbital Orientations of Exoplanets: HAT-P-4b is Prograde and HAT-P-14b is Retrograde," The Astronomical Journal, 141, 63.

 

       We present observations of the Rossiter-McLaughlin effect for two exoplanetary systems, revealing the orientations of their orbits relative to the rotation axes of their parent stars. HAT-P-4b is prograde, with a sky-projected spin-orbit angle of λ = -4.9 ± 11.9 deg. In contrast, HAT-P-14b is retrograde, with λ = 189.1 ± 5.1 deg. These results conform with a previously noted pattern among the stellar hosts of close-in giant planets: hotter stars have a wide range of obliquities and cooler stars have low obliquities. This, in turn, suggests that three-body dynamics and tidal dissipation are responsible for the short-period orbits of many exoplanets. In addition, our data revealed a third body in the HAT-P-4 system, which could be a second planet or a companion star.

 

Wittenmyer, R.A., Tinney, C.G., O'Toole, S.J., Jones, H.R.A., Butler, R.P., Carter, B.D., Bailey, J., 2011, "On the Frequency of Jupiter Analogs," The Astrophysical Journal, 727, 102.

 

       The Anglo-Australian Planet Search has now accumulated 12 years of radial-velocity data with long-term instrumental precision better than 3 m s^.1. In this paper, we expand on earlier simulation work, to probe the frequency of near-circular, long-period gas-giant planets residing at orbital distances of 3-6 AU.the so-called Jupiter analogs. We present the first comprehensive analysis of the frequency of these objects based on radial-velocity data. We find that 3.3% of stars in our sample host Jupiter analogs; detailed, star-by-star simulations show that no more than 37% of stars host a giant planet between 3 and 6 AU.

 

 

Wouters, B., Riva, R.E.M., Lavallé D.A., Bamber, J.L., 2011, "Seasonal variations in sea level induced by continental water mass: First results from GRACE," Geophysical Research Letters, 38, 03303.

 

       Variations in the Earth's water cycle are commonly quantified by their effect on global mean sea-level. However, the interaction between passive adjustment of the ocean to changes in gravitational attraction due to mass redistribution, the related deformation of the solid Earth and disturbances in the Earth's rotation vector will yield a distribution that is more complicated than a uniform rise or fall of the ocean's surface. In this study, we present the first estimates of seasonal changes in passive sea-level (which we define as the height difference between the sea surface at rest and ocean floor, excluding steric and dynamical effects) based on direct observations of surface mass redistribution, made by the Gravity Recovery and Climate Experiment (GRACE) between 2003 and 2010. We show that this .selfgravitation-effect. causes seasonal variations of the sea-level of up to 1 cm . comparable to the amplitude of the long-period tides . and that inclusion in numerical ocean models results in a better agreement between observed and modelled ocean bottom pressure variations, particularly in coastal zones.

 

 

 

Wright, D.J., ChenéA.-N., De Cat, P., Marois, C., Mathias, P., Macintosh, B., Isaacs, J., Lehmann, H., Hartmann, M., 2011, "Determination of the Inclination of the Multi-planet Hosting Star HR 8799 Using Asteroseismology," The Astrophysical Journal, 728, L20.

 

       Direct imaging of the HR 8799 system was a major achievement in the study of exoplanets. HR 8799 is a g Doradus variable and asteroseismology can provide an independent constraint on the inclination. Using 650 high signal-to-noise, high-resolution, full visual wavelength spectroscopic observations obtained over two weeks at Observatoire de Haute Provence with the SOPHIE spectrograph, we find that the main frequency in the radial velocity data is 1.9875 day^.1. This frequency corresponds to the main frequency as found in previous photometric observations. Using the FAMIAS software to identify the pulsation modes, we find that this frequency is a prograde ell = 1 sectoral mode and obtain the constraint that inclination i >~ 40°.

 

 

Xia, Y., Luo, Y.-J., Zhao, H.-B., Li, G.-Y., 2011, "Accessibility of Main-belt Asteroids and Trajectory Design for Multi-target Exploration," Chinese Astronomy and Astrophysics, 35, 71-81.

 

       The mission designed to explore asteroids has nowadays become a hot spot of deep space exploration, and the accessibility of the explored objects is the most important problem to make clear. The number of asteroids is large, and it needs an enormous quantity of calculations to evaluate the accessibility for all asteroids. In this paper, based on the direct transfer strategy, we have calculated the accessibility for the different regions of the solar system and compared it with the distribution of asteroids. It is found that most main-belt asteroids are accessible by the direct transfer orbit with the launch energy of C₃ = 50 km²/s², and that with an additional small velocity correction, the designed trajectory is able to realize the multi-target flyby mission. Such a kind of multi-target flyby can reach the same effect of the orbit manoeuvre in the ΔV-EGA trajectory scheme. Being assisted by the earth's gravity, the accompanying flight with asteroids or the exploration of more distant asteroids can be realized with a lower energy. In the end, as an example, a trajectory scheme is given, in which the probe flies by multiple main-belt asteroids at first, then with the assistance of the earth's gravity, it makes the accompanying flight to a more distant asteroid.

 

 

Xu, G., Tianhe, X., Chen, W., Yeh, T.-K., 2011, "Analytical solution of a satellite orbit disturbed by atmospheric drag," Monthly Notices of the Royal Astronomical Society, 410, 654-662.

 

       In this paper, we derive the analytical solution of a satellite orbit disturbed by atmospheric drag. The disturbance force vector is first transformed and rotated to the orbital frame so that it can be used in the simplified Gaussian equations of satellite motion. Then, the force vector is expanded to triangular functions of the Keplerian angular elements and the disturbances are separated into three parts: short-periodic terms with triangular functions of M, long-periodic terms with triangular functions of (ω, i) and secular terms [non-periodic functions of (a, e)] with a program using mathematical symbolic operation software. The integrations are then carried out with respect to M, (ω, i) and t, respectively, to obtain the analytical solutions of satellite orbits disturbed by atmospheric drag. Some interesting conclusions are obtained theoretically. The atmospheric disturbance force is not a function of Ω. The semimajor axis a of the orbital ellipse is reduced in a constant and strong manner by the air disturbance; the shape of the ellipse (eccentricity e) changes towards a more circular orbit in a linear and weak manner. The right ascension of the ascending node Ω and the mean anomaly M are influenced by the disturbance only short periodically.

 

Xu, G., Xu, T., Yeh, T.-K., Chen, W., 2011, "Analytical solution of a satellite orbit disturbed by lunar and solar gravitation," Monthly Notices of the Royal Astronomical Society, 410, 645-653.

 

       In this paper, we derive to the second order (5 ×10^-6) the analytical solution of a satellite orbit disturbed by the lunar gravitational force. The force vector is first expanded to omit terms smaller than the third order (10^-9). Then, four terms of potential functions are derived from the expanded force vector and set into the Lagrangian equations of satellite motion to obtain the theoretical solutions. For the first term of the potential functions, the solutions are derived directly. For the second term, mathematical expansions and transformations are used to separate disturbances into three parts: short-periodic terms with triangular functions of M, long-periodic terms with triangular functions of (ω, i, Ω) and secular terms with non-periodic functions of (a, e). The integrations are then carried out with respect to M, (ω, i, Ω) and t, to obtain the analytical solutions of satellite orbits with a program using mathematical symbolic operation software. The third potential function differs from the second by a factor and the fourth is simpler than the second. Therefore, the solutions are derived similarly using slightly modified programs, respectively. The results show that only two Keplerian elements (ω, M) are linearly perturbed by lunar gravitation; that is, the lunar attracting force will cause a linear regression (delay) of the perigee (orientation of the ellipse) and a linear delay of the position (mean anomaly) on an Earth satellite. The Keplerian element a (semimajor axis of the ellipse) is not perturbed long periodically as the others. The derived solutions are also valid for solar and planetary gravitational disturbances. Because of the distance differences between the Moon, the Sun and the planets to the Earth or an Earth satellite, the solutions are of third and fourth orders for solar and planetary gravitational disturbances on an Earth satellite, respectively.

 

 

Yamada, K., Asada, H., 2011, "Uniqueness of collinear solutions for the relativistic three-body problem," Physical Review D, 83, 24040.

 

       Continuing work initiated in an earlier publication [Yamada, Asada, Phys. Rev. DPRVDAQ1550-7998 82, 104019 (2010)10.1103/PhysRevD.82.104019], we investigate collinear solutions to the general relativistic three-body problem. We prove the uniqueness of the configuration for given system parameters (the masses and the end-to-end length). First, we show that the equation determining the distance ratio among the three masses, which has been obtained as a seventh-order polynomial in the previous paper, has at most three positive roots, which apparently provide three cases of the distance ratio. It is found, however, that, even for such cases, there exists one physically reasonable root and only one, because the remaining two positive roots do not satisfy the slow-motion assumption in the post-Newtonian approximation and are thus discarded. This means that, especially for the restricted three-body problem, exactly three positions of a third body are true even at the post-Newtonian order. They are relativistic counterparts of the Newtonian Lagrange points L₁, L₂, and L₃. We show also that, for the same masses and full length, the angular velocity of the post-Newtonian collinear configuration is smaller than that for the Newtonian case. Provided that the masses and angular rate are fixed, the relativistic end-to-end length is shorter than the Newtonian one.

 

 

Yamashita, K., Maruyama, S., Yamakawa, A., Nakamura, E., 2011, "Erratum: "53Mn-53Cr Chronometry of CB Chondrite: Evidence for Uniform Distribution of 53Mn in the Early Solar System" (2010, ApJ, 723, 20)," The Astrophysical Journal, 728, 165.

 

       Not Available

 

 

Yeager, K.E., Eberle, J., Cuntz, M., 2011, "On the ejection of Earth-mass planets from the habitable zones of the solar twins HD 20782 and HD 188015," International Journal of Astrobiology, 10, 1-13.

 

       We provide a detailed statistical study of the ejection of fictitious Earth-mass planets from the habitable zones of the solar twins HD 20782 and HD 188015. These systems possess a giant planet that crosses into the stellar habitable zone, thus effectively thwarting the possibility of habitable terrestrial planets. In the case of HD 188015, the orbit of the giant planet is essentially circular, whereas in the case of HD 20782, it is extremely elliptical. As starting positions for the giant planets, we consider both the apogee and perigee positions, whereas the starting positions of the Earth-mass planets are widely varied. For the giant planets, we consider models based on their minimum masses as well as models where the masses are increased by 30%. Our simulations indicate a large range of statistical properties concerning the ejection of the Earth-mass planets from the stellar habitable zones. For example, it is found that the ejection times for the Earth-mass planets from the habitable zones of HD 20782 and HD 188015, originally placed at the centre of the habitable zones, vary by a factor of ~200 and ~1500, respectively, depending on the starting positions of the giant and terrestrial planets. If the mass of the giant planet is increased by 30%, the variation in ejection time for HD 188015 increases to a factor of ~6000. However, the short survival times of any Earth-mass planets in these systems are of no surprise. It is noteworthy, however, that considerable differences in the survival times of the Earth-mass planets are found, which may be relevant for establishing guidelines of stability for systems with less intrusive giant planets.

 

 

Zakamska, N.L., Pan, M., Ford, E.B., 2011, "Observational biases in determining extrasolar planet eccentricities in single-planet systems," Monthly Notices of the Royal Astronomical Society, 410, 1895-1910.

 

       We investigate potential biases in the measurements of exoplanet orbital parameters obtained from radial velocity observations for single-planet systems. We create a mock catalogue of radial velocity data, choosing input planet masses, periods and observing patterns from actual radial velocity surveys and varying input eccentricities. We apply Markov chain Monte Carlo simulations and compare the resulting orbital parameters to the input values. We find that a combination of the effective signal-to-noise ratio of the data, the maximal gap in phase coverage, and the total number of periods covered by observations is a good predictor of the quality of derived orbit parameters. As eccentricity is positive definite, we find that eccentricities of planets on nearly circular orbits are preferentially overestimated, with typical bias of one to two times the median eccentricity uncertainty in a survey (e.g. 0.04 in the Butler et al. catalogue). When performing population analysis, we recommend using the mode of the marginalized posterior eccentricity distribution to minimize potential biases. While the Butler et al. catalogue reports eccentricities below 0.05 for just 17 per cent of single-planet systems, we estimate that the true fraction of e≤ 0.05 orbits is about f_0.05= 38 ± 9 per cent. For planets with P > 10 d, we find f_0.05= 28 ± 8 per cent versus 10 per cent from Butler et al. These planets either never acquired a large eccentricity or were circularized following any significant eccentricity excitation.

 

 

Zhang, L., Zhao, G., 2011, "The identification of comets in Chinese historical records," Science in China G: Physics and Astronomy, 54, 150-155.

 

       The historical records of astronomical phenomena may play a significant role in comet identification. Getting an accurate result is based on many factors, of which the calculation of orbital elements is the most important. This paper presents a "Cross Reference" method in which the perturbation of Jupiter is the only considered factor used to attempt an efficient way of comet identification with ancient Chinese historical records. In this method, the records before and after the calculated result from orbital determination within the error range are compared with the historical records to find the correlated perihelion time, and then, with five other orbital elements at the perihelion time, the ephemeris is calculated. If the calculated ephemeris matches the historical records, it is concluded that the comet determined by orbital calculation is the same as the one recorded in history. With this method, three comets with four historical records have already been found.

 

 

Zhou, L.-Y., Dvorak, R., Sun, Y.-S., 2011, "The dynamics of Neptune Trojans - II. Eccentric orbits and observed objects," Monthly Notices of the Royal Astronomical Society, 410, 1849-1860.

 

       In a previous paper, we presented a global view of the stability of Neptune Trojans (NTs hereafter) on inclined orbits. As the continuation of the investigation, we discuss in this paper the dependence of the stability of NT orbits on the eccentricity. For this task, high-resolution dynamical maps are constructed using the results of extensive numerical integrations of orbits initialized on fine grids of initial semimajor axis (a₀) versus eccentricity (e₀). The extensions of regions of stable orbits on the (a₀, e₀) plane at different inclinations are shown. The maximum eccentricities of stable orbits in the three most stable regions at low (0°, 12°), medium (22°, 36°) and high (51°, 59°) inclination are found to be 0.10, 0.12 and 0.04, respectively. The fine structures in the dynamical maps are described. Via the frequency-analysis method, the mechanisms that portray the dynamical maps are revealed. The secondary resonances, at the frequency of the librating resonant angle λ-λ₈ and the frequency of the quasi 2:1 mean-motion resonance (MMR hereafter) between Neptune and Uranus, are found to be deeply involved in the motion of NTs. Secular resonances are detected and they also contribute significantly to the triggering of chaos in the motion. In particular, the effects of the secular resonance ν₈, ν₁₈ are clarified.

 

We also investigate the orbital stabilities of six observed NTs by checking the orbits of hundreds of clones generated within the observing error bars. We conclude that four of them are deeply inside the stable region, with 2001 QR322 and 2005 TO74 being the exceptions. 2001 QR322 is in the close vicinity of the most significant secondary resonance. 2005 TO74 is located close to the boundary separating stable orbits from unstable ones, and it may be influenced by a secular resonance. This article was published online on 2010 October 25. Some errors were subsequently identified. This notice is included in the online and print versions to indicate that both have been corrected on 2010 November 2.