We present new results in modeling the interiors of Giant Planets (GP) and Brown Dwarfs (BD). In general models of the interior rely on equation of state data for planetary materials which have considerable uncertainties in the high-pressure domain. Our calculations are based on ab initio equation of state (EOS) data for hydrogen, helium, hydrogen-helium mixtures and water as the representative of all heavier elements or ices using finite-temperature density functional theory molecular dynamics (FT-DFT-MD) simulations. We compare results for the BD Gliese 229B calculated with Saumon-Chabrier-Van Horn EOS (SCVH95) and our EOS data.

Hot-Jupiters are known to be dark in visible bandpasses, mainly because of the alkali metal absorption lines and TiO and VO molecular absorption bands. The outstanding quality of the Kepler mission photometry allows a detection (or non-detection upper limits on) giant planet secondary eclipses at visible wavelengths. We present such measurements on published planets from Kepler Q1 data. We then explore how to disentangle between the planetary thermal emission and the reflected light components that can both contribute to the detected signal in the Kepler bandpass. We finally mention how different physical processes can lead to a wide variety of hot-Jupiters albedos.

We present a re-analysis of archival HST/NICMOS transmission spectroscopy of the exoplanet system, HD 189733, from which detections of several molecules have been claimed. As expected, we can replicate the transmission spectrum previously published when we use an identical model for the systematic effects, although the uncertainties are larger as we use a residual permutation algorithm in an effort to account for instrumental systematics. We also find that the transmission spectrum is considerably altered when slightly changing the instrument model, and conclude that the NICMOS transmission spectrum is too dependent on the method used to remove systematics to be considered a robust detection of molecular species, given that there is no physical reason to believe that the baseline flux should be modelled as a linear function of any chosen set of parameters.

We model the polarization in the system HD 189733 resulting from the planetary transit. This system has a short-period (2.2d) Jupiter-like planet with the radii ratio Rp/R* = 0.148, orbiting at the distance of 0.031 AU around the star.

We calculated the polarization of the system HD189733 to be 0.022% at the limb, which is consistent with the recent observational data. We suggest the shapes of the polarization parameters curves to be used for deriving the planet orbit inclination at the near limb transits as an alternative to standard transit method.

For the solar sytem giant planets the measurement of the gravitational moments J2 and J4 provided valuable information about the interior structure. However, for extrasolar planets the gravitational moments are not accessible. Nevertheless, an additional constraint for extrasolar planets can be obtained from the tidal Love number k2, which, to first order, is equivalent to J2. k2 quantifies the quadrupolic gravity field deformation at the surface of the planet in response to an external perturbing body and depends solely on the planet's internal density distribution. On the other hand, the inverse deduction of the density distribution of the planet from k2 is non-unique. The Love number k2 is a potentially observable parameter that can be obtained from tidally induced apsidal precession of close-in planets (Ragozzine & Wolf 2009) or from the orbital parameters of specific two-planet systems in apsidal alignment (Mardling 2007). We find that for a given k2, a precise value for the core mass cannot be derived. However, a maximum core mass can be inferred which equals the core mass predicted by homogeneous zero metallicity envelope models. Using the example of the extrasolar transiting planet HAT-P-13b we show to what extend planetary models can be constrained by taking into account the tidal Love number k2.

During the last few years, observations have yielded an abundant population of short-period planets under 15 Earth masses. Among those, hot terrestrial exoplanets represent a key population to study the survival of dense atmospheres close to their parent star. Thermal emission from exoplanets orbiting low-mass stars will be observable with the next generation of infrared telescopes, in particular the JWST. In order to constrain planetary and atmospheric properties, we have developed models to simulate the variation of the infrared emission along the path of the orbit (IR phase curve) for both airless planets and planets with dense atmospheres. Here, we focus on airless planets and present preliminary results on the influence of orbital elements, planet rotation, surface properties and observation geometry. Then, using simulated noisy phase curves, we test the retrieval of planets' properties and identify the degeneracies.

Secondary eclipse observations of exoplanets at near-infrared wavelengths are important to constrain the energy budgets of hot-Jupiters, since they probe the radiation from the planet's atmosphere at the peak of the spectral energy distribution. Since this wavelength range is accesible from the ground, we have started the GROUnd-based Secondary Eclipse (GROUSE) project. As part of the GROUSE project, we target a sample of hot-Jupiters at near-infrared and optical wavelengths. Planets include TrES-3b, HAT-P-1, WASP-18b and WASP-33b.

We present new photometric and astrometric data available for S Ori 70 and 73, the two T-type planetary-mass member candidates in the σ Orionis cluster (~3 ± 2 Myr, d~360 pc). S Ori 70 (J ~ 19.9 mag) has a spectral type of T5.5 ± 1.0 measured from published near-infrared spectra, while no spectroscopic data are available for S Ori 73 (J ~ 21 mag). We estimate the spectral type of S Ori 73 by using J, H, and CH4off (λc=1.575 μm, Δλ=0.112 μm) photometry and comparing the H-CH4off index of S Ori 73 with the colors of field stars and brown dwarfs of spectral types in the range F to late T. The locations of S Ori 70 and 73 in the J-H vs H-CH4off color-color diagram are consistent with spectral types T8 ± 1 and T4 ± 1, respectively. Proper motion measurements of the two sources are larger than the motion of the central σ Ori star, making their cluster membership somehow uncertain.

The detection of sodium absorption during primary transit implies the presence of an atmosphere around an extrasolar planet. WASP-17b (Anderson et al. 2010a) is the least dense known planet, with a radius twice that of Jupiter. It orbits an F6-type star, and its low gravity gives its atmosphere a very large scale height. The sodium transit depth is expected to be 4.1 – 5.2 times deeper than for HD 209458b (Seager & Sasselov 2000). We obtained 24 spectra with the GIRAFFE spectrograph on the VLT, 8 during transit. We measured the flux in the sodium doublet at 5889.95 Å and 5895.92 Å using bandpasses 0.75, 1.5, 3.0 and 6.0 Å. We find a transit depth of 0.55±0.13% at 1.5 Å (4.3σ). WASP-17b therefore has an atmosphere which is depleted in sodium compared to predictions.

QS Vir is an eclipsing cataclysmic variable with 3.618 hrs orbital period. This system has the interesting characteristics that it does not show mass transfer between the components through the L1 Lagrangian point and shows a complex orbital period variation history. Qian et al. (2010) associated the orbital period variations to the presence of a giant planet in the system plus angular momentum loss via magnetic braking. Parsons et al. (2010) obtained new eclipse timings and observed that the orbital period variations associated to a hypothetical giant planet disagree with their measurements and concluded that the decrease in orbital period is part of a cyclic variation with period ~16 yrs. In this work, we present 28 new eclipse timings of QS Vir and suggest that the orbital period variations can be explained by a model with two circumbinary bodies. The best fitting gives the lower limit to the masses M1 sin(i) ~ 0.0086 M⊙ and M2 sin(i) ~ 0.054 M⊙; orbital periods P1 ~ 14.4 yrs and P2 ~ 16.99 yrs, and eccentricities e1 ~ 0.62 and e2~0.92 for the two external bodies. Under the assumption of coplanarity among the two external bodies and the inner binary, we obtain a giant planet with ~0.009 M⊙ and a brown dwarf with ~ 0.056 M⊙ around the eclipsing binary QS Vir.

The migration of protoplanets in discs not only depends on the thermodynamics of the ambient disc but also on the orbital parameters of the embedded planet. In the fully radiative regime, planets can migrate outward if their orbital parameters fit in a very small range. We simulate planets in fully radiative discs (and isothermal discs - for reference) and determine the influence of the orbital parameters (a, e and i) and the planetary mass on the migration time scale and direction.

A close-in massive planet affects the angular momentum of its host star through tidal and magnetic interactions. The transiting planets allow us to study the distribution of the spin and orbital angular momenta in star-planet systems. Considering a sample of about 70 systems, we find that stars having an effective temperature between 6000 and 6700 K and a rotation period shorter than 10 days show a rotation synchronized with the orbit of their hot Jupiters or have a rotation period twice the orbital period of their planets. Such rotational behaviours cannot be explained on the basis of tidal interactions alone. Besides, the gyrochronology relationship for those systems holds if an angular momentum loss rate smaller by about 30 percent than in stars without hot Jupiters is assumed.

Different migration scenario of two giant planets may play a major role in forming the diverse resonant planetary configurations. The studies on the HD 128311 and HD 73526 systems show that two gas giants are captured in a 2:1 resonance but not in apsidal corotation, because one of the resonant argument circulates over the dynamical evolution. Herein we explore potential scenarios to produce the 2:1 librating-circulating resonance configuration. In the simulations, we find that both colliding or scattering events at early stage of dynamical evolution can induce the configurations trapped into resonance. In this sense, the librating-circulating resonance configuration is more likely to form by a hybrid mechanism of scattering and collision.

In a recently published paper Matsumura et al. (2010) (hereafter M10), we have studied the evolution of three-planet systems in dissipating gas disks by using a hybrid N-body and one-dimensional gas disk evolution code. In this article, we highlight some results which are only briefly mentioned in M10.

Studies of the structure and evolution of protoplanetary disks are important for understanding star and planet formation. Here, we present the direct image of an interacting binary protoplanetary system. Both circumprimary and circumsecondary disks are resolved in the near-infrared. There is a bridge of infrared emission connecting the two disks and a long spiral arm extending from the circumprimary disk. Numerical simulations show that the bridge corresponds to gas flow and a shock wave caused by the collision of gas rotating around the primary and secondary stars. Fresh material streams along the spiral arm, consistent with the theoretical scenarios where gas is replenished from a circummultiple reservoir.

We investigate the motion of a two-planet coplanar system under the combined effects of mutual interaction and tidal dissipation. The secular behavior of the system is analyzed using two different approaches, restricting to the case of a more massive outer planet. First, we solve the exact equations of motion through the numerical simulation of the system evolution. We also compute the stationary solutions of the mean equations of motion based on a Hamiltonian formalism. An application to the real system CoRoT-7 is investigated.

We present the photometric analysis of 4 transits of the exoplanet WASP-4b, obtained with the Baade 6.5m telescope, one of the two Magellan telescopes at Las Campanas. The light curves have a photometric precision of 0.5 mmag and a time sampling of 30s. This high precision has allowed us to detect several “spot anomalies”: temporary brightenings due to the occultation of a starspot on the transit chord. By analyzing these anomalies we find the sky-projected stellar obliquity to be λ = 1°+12°−14°. The small value suggests that the planet migration mechanism preserved the initially low obliquity, or that tidal evolution has realigned the system.

Outward migration of planets due to Roche lobe overflow may play an important role in producing the presently observed distribution of planet parameters. We suggest that many of the currently known short period planets may have already migrated into the Roche distance from the star, and then deposited at their current semi-major axes by being migrated outwards due to angular momentum transfer from an episode of Roche lobe overflow (RLO). This RLO outward migration (RLOOM) could be sustained in the region where planetary radius increases with decreasing mass. We are modeling how RLOOM may leave what kind of planet parameter statistics. This modeling seeks to predict what observable signs of RLOOM there may be. Overflow of planetary mass may leave behind characteristic hot dust and gas as well as produce luminous signatures.

We performed 3D MHD numerical simulations of planet migration in stratified disks using the Godunov code PLUTO (Mignone et al. 2007). The disk is invaded by turbulence generated by the magnetorotational instability (MRI). We study the migration for planets with different mass to primary mass ratio. The migration of the low-mass planet (q=Mp/Ms=10−5) is dominated by random fluctuations in the torque and there is no defined direction of migration on timescales of 100 orbits. The intermediate-mass planet (q=Mp/Ms=10−4) can experience systematic outwards migration that was sustained for the times we were able to simulate.

Due to the gravitational influence of density fluctuations driven by magneto-rotational instability in the gas disk, planetesimals and protoplanets undergo diffusive radial migration as well as changes of other orbital properties. The magnitude of the effect on particle orbits has important consequences for planet formation scenarios. We use the local-shearing-box approximation to simulate an ideal, isothermal, magnetized gas disk with vertical density stratification and simultaneously evolve numerous massless particles moving under the gravity of the gas and the host star. Although the results converge with resolution for fixed box dimensions, we find there exists no convergence of the response of the particles to the gravity of the gas against the horizontal box size, up to 16 disk scale heights. This lack of convergence indicate that caution should be exercised when interpreting local-shearing-box models involving gravitational physics of magneto-rotational turbulence.