Abstract: New transiting planet candidates are identified in sixteen months (May 2009 - September 2010) of data from the Kepler spacecraft. Nearly five thousand periodic transit-like signals are vetted against astrophysical and instrumental false positives yielding 1,091 viable new planet candidates, bringing the total count up to over 2,300. Improved vetting metrics are employed, contributing to higher catalog reliability. Most notable is the noise-weighted robust averaging of multi-quarter photo-center offsets derived from difference image analysis which identifies likely background eclipsing binaries. Twenty-two months of photometry are used for the purpose of characterizing each of the new candidates. Ephemerides (transit epoch, T_0, and orbital period, P) are tabulated as well as the products of light curve modeling: reduced radius (Rp/R*), reduced semi-major axis (d/R*), and impact parameter (b). The largest fractional increases are seen for the smallest planet candidates (197% for candidates smaller than 2Re compared to 52% for candidates larger than 2Re) and those at longer orbital periods (123% for candidates outside of 50-day orbits versus 85% for candidates inside of 50-day orbits). The gains are larger than expected from increasing the observing window from thirteen months (Quarter 1-- Quarter 5) to sixteen months (Quarter 1 -- Quarter 6). This demonstrates the benefit of continued development of pipeline analysis software. The fraction of all host stars with multiple candidates has grown from 17% to 20%, and the paucity of short-period giant planets in multiple systems is still evident. The progression toward smaller planets at longer orbital periods with each new catalog release suggests that Earth-size planets in the Habitable Zone are forthcoming if, indeed, such planets are abundant.

Abstract: Within the next few years, GAIA and several instruments aiming to image extrasolar planets will be ready. In parallel, low-mass planets are being sought around red dwarfs, which offer more favourable conditions, for both radial velocity detection and transit studies, than solar-type stars. In this paper, the authors of a model atmosphere code that has allowed the detection of water vapour in the atmosphere of hot Jupiters review recent advances in modelling the stellar to substellar transition. The revised solar oxygen abundances and cloud model allow the photometric and spectroscopic properties of this transition to be reproduced for the first time. Also presented are highlight results of a model atmosphere grid for stars, brown dwarfs and extrasolar planets.

Abstract: We report the distribution of planets as a function of planet radius, orbital period, and stellar effective temperature for orbital periods less than 50 days around solar-type (GK) stars. These results are based on the 1235 planets (formally “planet candidates”) from the Kepler mission that include a nearly complete set of detected planets as small as 2 R⊕. For each of the 156,000 target stars, we assess the detectability of planets as a function of planet radius, Rp, and orbital period, P, using a measure of the detection efficiency for each star. We also correct for the geometric probability of transit, R⋆/a. We consider first Kepler target stars within the “solar subset” having Teff = 4100–6100 K, log g = 4.0–4.9, and Kepler magnitude Kp < 15 mag, i.e., bright, main-sequence GK stars. We include only those stars having photometric noise low enough to permit detection of planets down to 2 R⊕. We count planets in small domains of Rp and P and divide by the included target stars to calculate planet occurrence in each domain. The resulting occurrence of planets varies by more than three orders of magnitude in the radius–orbital period plane and increases substantially down to the smallest radius (2 R⊕) and out to the longest orbital period (50 days, ∼0.25 AU) in our study. For P < 50 days, the distribution of planet radii is given by a power law, df/dlog R = kRRα with kR = 2.9+0.5− 0.4, α = −1.92 ± 0.11, and R ≡ Rp/R⊕. This rapid increase in planet occurrence with decreasing planet size agrees with the prediction of core-accretion formation but disagrees with population synthesis models that predict a desert at super-Earth and Neptune sizes for close-in orbits. Planets with orbital periods shorter than 2 days are extremely rare; for Rp > 2 R⊕ we measure an occurrence of less than 0.001 planets per star. For all planets with orbital periods less than 50 days, we measure occurrence of 0.130 ± 0.008, 0.023 ± 0.003, and 0.013 ± 0.002 planets per star for planets with radii 2–4, 4–8, and 8–32 R⊕, in agreement with Doppler surveys. We fit occurrence as a function of P to a power-law model with an exponential cutoff below a critical period P0. For smaller planets, P0 has larger values, suggesting that the “parking distance” for migrating planets moves outward with decreasing planet size. We also measured planet occurrence over a broader stellar Teff range of 3600–7100 K, spanning M0 to F2 dwarfs. Over this range, the occurrence of 2–4 R⊕ planets in the Kepler field increases with decreasing Teff, with these small planets being seven times more abundant around cool stars (3600–4100 K) than the hottest stars in our sample (6600–7100 K).

Abstract: The abundance of heavy elements (metallicity) in the photospheres of stars similar to the Sun provides a 'fossil' record of the chemical composition of the initial protoplanetary disk. Metal-rich stars are much more likely to harbour gas giant planets(1-4), supporting the model that planets form by accumulation of dust and ice particles(5). Recent ground-based surveys suggest that this correlation is weakened for Neptunian-sized planets(4,6-9). However, how the relationship between size and metallicity extends into the regime of terrestrial-sized exoplanets is unknown. Here we report spectroscopic metallicities of the host stars of 226 small exoplanet candidates discovered by NASA's Kepler mission(10), including objects that are comparable in size to the terrestrial planets in the Solar System. We find that planets with radii less than four Earth radii form around host stars with a wide range of metallicities (but on average a metallicity close to that of the Sun), whereas large planets preferentially form around stars with higher metallicities. This observation suggests that terrestrial planets may be widespread in the disk of the Galaxy, with no special requirement of enhanced metallicity for their formation.

Abstract: As planets form and grow within gaseous protoplanetary disks, the mutual gravitational interaction between the disk and planet leads to the exchange of angular momentum and migration of the planet. We review current understanding of disk-planet interactions, focusing in particular on physical processes that determine the speed and direction of migration. We describe the evolution of low-mass planets embedded in protoplanetary disks and examine the influence of Lindblad and corotation torques as a function of the disk properties. The role of the disk in causing the evolution of eccentricities and inclinations is also discussed. We describe the rapid migration of intermediate-mass planets that may occur as a runaway process and examine the transition to gap formation and slower migration driven by the viscous evolution of the disk for massive planets. The roles and influence of disk self-gravity and magnetohydrodynamic turbulence are discussed in detail, as a function of the planet mass, as is the evolution...

Abstract: A common origin for the Moon and Earth is required by their identical isotopic composition. However, simulations of the current giant impact hypothesis for Moon formation find that most lunar material originated from the impactor, which should have had a different isotopic signature. Previous Moon-formation studies assumed that the angular momentum after the impact was similar to that of the present day; however, Earth-mass planets are expected to have higher spin rates at the end of accretion. Here, we show that typical last giant impacts onto a fast-spinning proto-Earth can produce a Moon-forming disk derived primarily from Earth’s mantle. Furthermore, we find that a faster-spinning early Earth-Moon system can lose angular momentum and reach the present state through an orbital resonance between the Sun and Moon.

Abstract: Determining the source(s) of hydrogen, carbon, and nitrogen accreted by Earth is important for understanding the origins of water and life and for constraining dynamical processes that operated during planet formation. Chondritic meteorites are asteroidal fragments that retain records of the first few million years of solar system history. The deuterium/hydrogen (D/H) values of water in carbonaceous chondrites are distinct from those in comets and Saturn’s moon Enceladus, implying that they formed in a different region of the solar system, contrary to predictions of recent dynamical models. The D/H values of water in carbonaceous chondrites also argue against an influx of water ice from the outer solar system, which has been invoked to explain the nonsolar oxygen isotopic composition of the inner solar system. The bulk hydrogen and nitrogen isotopic compositions of CI chondrites suggest that they were the principal source of Earth’s volatiles.

Abstract: We report on the orbital architectures of Kepler systems having multiple planet candidates identified in the analysis of data from the first six quarters of Kepler data and reported by Batalha et al (2013) These data show 899 transiting planet candidates in 365 multiple-planet systems and provide a powerful means to study the statistical properties of planetary systems Using a generic mass-radius relationship, we find that only two pairs of planets in these candidate systems (out of 761 pairs total) appear to be on Hill-unstable orbits, indicating ~96% of the candidate planetary systems are correctly interpreted as true systems We find that planet pairs show little statistical preference to be near mean-motion resonances We identify an asymmetry in the distribution of period ratios near first-order resonances (eg, 2:1, 3:2), with an excess of planet pairs lying wide of resonance and relatively few lying narrow of resonance Finally, based upon the transit duration ratios of adjacent planets in each system, we find that the interior planet tends to have a smaller transit impact parameter than the exterior planet does This finding suggests that the mode of the mutual inclinations of planetary orbital planes is in the range 10-22 degrees, for the packed systems of small planets probed by these observations

Abstract: In the giant impact theory, the Moon formed from debris ejected into an Earth-orbiting disk by the collision of a large planet with the early Earth. Prior impact simulations predict that much of the disk material originates from the colliding planet. However, Earth and the Moon have essentially identical oxygen isotope compositions. This has been a challenge for the impact theory, because the impactor’s composition would have likely differed from that of Earth. We simulated impacts involving larger impactors than previously considered. We show that these can produce a disk with the same composition as the planet’s mantle, consistent with Earth-Moon compositional similarities. Such impacts require subsequent removal of angular momentum from the Earth-Moon system through a resonance with the Sun as recently proposed.

Abstract: A fundamental determinant of climate and life on our planet is the solar radiation (sunlight) incident at the Earth's surface. Any change in this precious energy source affects our habitats profoundly. Until recently, for simplicity and lack of better knowledge, the amount of solar radiation received at the Earth's surface was assumed to be stable over the years. However, there is increasing observational evidence that this quantity undergoes significant multidecadal variations, which need to be accounted for in discussions of climate change and mitigation strategies. Coherent periods and regions with prevailing declines (“dimming”) and inclines (“brightening”) in surface solar radiation have been detected in the worldwide observational networks, often in accord with anthropogenic air pollution patterns. The present synthesis provides in a nutshell the main characteristics of this phenomenon, a conceptual framework for its causes, and an overview of potential environmental implications. The latest develop...

Abstract: In the solar system, the planets’ compositions vary with orbital distance, with rocky planets in close orbits and lower-density gas giants in wider orbits. The detection of close-in giant planets around other stars was the first clue that this pattern is not universal and that planets’ orbits can change substantially after their formation. Here, we report another violation of the orbit-composition pattern: two planets orbiting the same star with orbital distances differing by only 10% and densities differing by a factor of 8. One planet is likely a rocky “super-Earth,” whereas the other is more akin to Neptune. These planets are 20 times more closely spaced and have a larger density contrast than any adjacent pair of planets in the solar system.

Abstract: Young and directly imaged exoplanets offer critical tests of planet-formation models that are not matched by radial velocity surveys of mature stars. These targets have been extremely elusive to date, with no exoplanets younger than 10-20 Myr and only a handful of direct-imaged exoplanets at all ages. We report the direct-imaging discovery of a likely (proto)planet around the young (~2 Myr) solar analog LkCa 15, located inside a known gap in the protoplanetary disk (a transitional disk). Our observations use non-redundant aperture masking interferometry at three epochs to reveal a faint and relatively blue point source (, K' – L' = 0.98 ± 0.22), flanked by approximately co-orbital emission that is red and resolved into at least two sources (, K' – L' = 2.7 ± 0.3; , K' – L' = 1.94 ± 0.16). We propose that the most likely geometry consists of a newly formed (proto)planet that is surrounded by dusty material. The nominal estimated mass is ~6 M Jup according to the 1 Myr hot-start models. However, we argue based on its luminosity, color, and the presence of circumplanetary material that the planet has likely been caught at its epoch of assembly, and hence this mass is an upper limit due to its extreme youth and flux contributed by accretion. The projected separations (71.9 ± 1.6 mas, 100.7 ± 1.9 mas, and 88.2 ± 1.8 mas) and deprojected orbital radii (16, 21, and 19 AU) correspond to the center of the disk gap, but are too close to the primary star for a circular orbit to account for the observed inner edge of the outer disk, so an alternative explanation (i.e., additional planets or an eccentric orbit) is likely required. This discovery is the first direct evidence that at least some transitional disks do indeed host newly formed (or forming) exoplanetary systems, and the observed properties provide crucial insight into the gas giant formation process.

Abstract: We present high-resolution, H-band, imaging observations, collected with Subaru/HiCIAO, of the scattered light from the transitional disk around SAO 206462 (HD 135344B). Although previous sub-mm imagery suggested the existence of the dust-depleted cavity at r approximates 46 AU, our observations reveal the presence of scattered light components as close as 0".2 (approx 28 AU) from the star. Moreover, we have discovered two small-scale spiral structures lying within 0".5 (approx 70 AU). We present models for the spiral structures using the spiral density wave theory, and derive a disk aspect ratio of h approx 0.1, which is consistent with previous sub-mm observations. This model can potentially give estimates of the temperature and rotation profiles of the disk based on dynamical processes, independently from sub-mm observations. It also predicts the evolution of the spiral structures, which can be observable on timescales of 10-20 years, providing conclusive tests of the model. While we cannot uniquely identify the origin of these spirals, planets embedded in the disk may be capable of exciting the observed morphology. Assuming that this is the case, we can make predictions on the locations and, possibly, the masses of the unseen planets. Such planets may be detected by future multi-wavelengths observations.

Abstract: This article reviews our current understanding of terrestrial planet formation. The focus is on computer simulations of the dynamical aspects of the accretion process. Throughout the review, we combine the results of these theoretical models with geochemical, cosmochemical, and chronological constraints to outline a comprehensive scenario of the early evolution of our solar system. Given that the giant planets formed first in the protoplanetary disk, we stress the sensitive dependence of the terrestrial planet accretion process on the orbital architecture of the giant planets and on their evolution. This suggests a great diversity among the terrestrial planet populations in extrasolar systems. Issues such as the cause for the different masses and accretion timescales between Mars and Earth and the origin of water (and other volatiles) on our planet are discussed in depth.

Abstract: Context. Transition disks are believed to be the final stages of protoplanetary disks, during which a forming planetary system or photoevaporation processes open a gap in the inner disk, drastically changing the disk structure. From theoretical arguments it is expected that dust growth, fragmentation and radial drift are strongly influenced by gas disk structure, and pressure bumps in disks have been suggested as key features that may allow grains to converge and grow efficiently.Aims. We want to study how the presence of a large planet in a disk influences the growth and radial distribution of dust grains, and how observable properties are linked to the mass of the planet.Methods. We combined two-dimensional hydrodynamical disk simulations of disk-planet interactions with state-of-the-art coagulation/fragmentation models to simulate the evolution of dust in a disk, which has a gap created by a massive planet. We computed images at different wavelengths and illustrated our results using the example of the transition disk LkCa15.Results. The gap opened by a planet and the long-range interaction between the planet and the outer disk create a single large pressure bump outside the planetary orbit. Millimeter-sized particles form and accumulate at the pressure maximum and naturally produce ring-shaped sub-millimeter emission that is long-lived because radial drift no longer depletes the large grain population of the disk. For large planet masses around 9 M Jup , the pressure maximum and, therefore, the ring of millimeter particles is located at distances that can be more than twice the star-planet separation, creating a large spatial separation between the gas inner edge of the outer disk and the peak millimeter emission. Smaller grains do get closer to the gap and we predict how the surface brightness varies at different wavelengths.

Abstract: We consider the evaporation of close-in planets by the star's intrinsic extreme-ultraviolet (EUV) and X-ray radiation. We calculate evaporation rates by solving the hydrodynamical problem for planetary evaporation including heating from both X-ray and EUV radiation. We show that most close-in planets (a < 0.1 au) are evaporating hydrodynamically, with the evaporation occurring in two distinct regimes: X-ray driven, in which the X-ray heated flow contains a sonic point, and EUV driven, in which the X-ray region is entirely sub-sonic. The mass-loss rates scale as LX/a2 for X-ray driven evaporation, and as for EUV driven evaporation at early times, with mass-loss rates of the order of 1010–1014 g s−1. No exact scaling exists for the mass-loss rate with planet mass and planet radius; however, in general evaporation proceeds more rapidly for planets with lower densities and higher masses. Furthermore, we find that in general the transition from X-ray driven to EUV driven evaporation occurs at lower X-ray luminosities for planets closer to their parent stars and for planets with lower densities. Coupling our evaporation models to the evolution of the high-energy radiation – which falls with time – we are able to follow the evolution of evaporating planets. We find that most planets start off evaporating in the X-ray driven regime, but switch to EUV driven once the X-ray luminosity falls below a critical value. The evolution models suggest that while ‘hot Jupiters’ are evaporating, they are not evaporating at a rate sufficient to remove the entire gaseous envelope on Gyr time-scales. However, we do find that close in Neptune mass planets are more susceptible to complete evaporation of their envelopes. Thus we conclude that planetary evaporation is more important for lower mass planets, particularly those in the ‘hot Neptune’/‘super Earth’ regime.

Abstract: The detection of carbon monoxide absorption in the spectrum of the extrasolar planet τ Bootis b, and its tracing of the change in the radial velocity of the planet, demonstrates that atmospheric characterization is possible for non-transiting planets. For more than a decade, the giant exoplanet orbiting τ Bootis has been closely observed. Its orbital inclination has been estimated on several occasions but with conflicting results. Now high-resolution infrared spectroscopy measurements from the Very Large Telescope array at the European Southern Observatory in Chile have been used to detect carbon monoxide in the thermal day-side atmosphere of the planet τ Bootis b while it was non-transiting. Previously a planet has had to be in transit across its host star for such observations to be made. From the spectral signature, the authors calculate an orbital inclination of about 44.5 degrees, and mass of about 5.95 times that of Jupiter. This new ground-based high-resolution spectroscopy technique should be generally applicable to the observation of atmospheres on other exoplanets. The giant planet orbiting τ Bootis (named τ Bootis b) was amongst the first extrasolar planets to be discovered1. It is one of the brightest exoplanets and one of the nearest to us, with an orbital period of just a few days. Over the course of more than a decade, measurements of its orbital inclination have been announced2 and refuted3, and have hitherto remained elusive4,5,6,7,8. Here we report the detection of carbon monoxide absorption in the thermal dayside spectrum of τ Bootis b. At a spectral resolution of ∼100,000, we trace the change in the radial velocity of the planet over a large range in phase, determining an orbital inclination of 44.5° ± 1.5° and a mass 5.95 ± 0.28 times that of Jupiter, demonstrating that atmospheric characterization is possible for non-transiting planets. The strong absorption signal points to an atmosphere with a temperature that is decreasing towards higher altitudes, in contrast to the temperature inversion inferred for other highly irradiated planets9,10. This supports the hypothesis that the absorbing compounds believed to cause such atmospheric inversions are destroyed in τ Bootis b by the ultraviolet emission from the active host star11.

Abstract: Capitalizing on the observational advantage oered by its tiny M dwarf host, we present HST/WFC3 grism measurements of the transmission spectrum of the super-Earth exoplanet GJ1214b. These are the rst published WFC3 observations of a transiting exoplanet atmosphere. After correcting for a ramp-like instrumental systematic, we achieve nearly photon-limited precision in these observations, nding the transmission spectrum of GJ1214b to be at between 1.1 and 1.7 m. Inconsistent with a cloud-free solar composition atmosphere at 8:2 , the measured achromatic transit depth most likely implies a large mean molecular weight for GJ1214b’s outer envelope. A dense atmosphere rules out bulk compositions for GJ1214b that explain its large radius by the presence of a very low density gas layer surrounding the planet. High-altitude clouds can alternatively explain the at transmission spectrum, but they would need to be optically thick up to 10 mbar or consist of particles with a range of sizes approaching 1 m in diameter. Subject headings: planetary systems: individual (GJ 1214b) | eclipses | techniques: spectroscopic

Abstract: Context. This is the fourth paper in a series showing the results of planet population synthesis calculations. In Paper I, we presented our methods. In Paper II, we compared the synthetic and the observed planetary population statistically. Paper III addressed the influences of the stellar mass on the population.Aims. Our goal in this fourth paper is to systematically study the effects of important disk properties, namely disk metallicity, mass, and lifetime on fundamental properties of planets like mass and semimajor axis.Methods. For a large number of protoplanetary disks that have properties following distributions derived from observations, we calculated a population of planets with our formation model. The model is based on the classical core accretion paradigm but self-consistently includes planet migration and disk evolution.Results. We find a very large number of correlations. Regarding the planetary initial mass function, metallicity, M disk , and τ disk play different roles. For high metallicities, giant planets are more frequent. For high M disk , giant planets are more massive. For long τ disk , giant planets are both more frequent and massive. At low metallicities, very massive giant planets cannot form, but otherwise giant planet mass and metallicity are nearly uncorrelated. In contrast, (maximum) planet masses and disk gas masses are correlated. The formation of giant planets is possible for initial planetesimal surface densities ΣS of at least 6 g/cm2 at 5.2 AU. The best spot for giant planet formation is at ~5 AU. In- and outside this distance, higher ΣS are necessary. Low metallicities can be compensated for by high M disk , and vice versa, but not ad infinitum. At low metallicities, giant planets only form outside the ice line, while giant planet formation occurs throughout the disk at high metallicities. The extent of migration increases with M disk and τ disk and usually decreases with metallicity. No clear correlation of metallicity and the semimajor axis distribution of giant planets exists because in low-metallicity disks, planets start farther out, but migrate more, while the contrary applies to high metallicities. The final semimajor axis distribution contains an imprint of the ice line. Close-in low mass planets have a lower mean metallicity than hot Jupiters. The frequency of giant planets varies approximately as M disk 1.2 and τ disk 2 . Conclusions. The properties of protoplanetary disks – the initial and boundary conditions for planet formation – are decisive for the properties of planets, and leave many imprints on the population.

Abstract: Gas-giant planets that form via core accretion might have very different characteristics from those that form via disk instability. Disk-instability objects are typically thought to have higher entropies, larger radii, and (generally) higher effective temperatures than core-accretion objects. In this paper, we provide a large set of models exploring the observational consequences of high-entropy (hot) and low-entropy (cold) initial conditions, in the hope that this will ultimately help to distinguish between different physical mechanisms of planet formation. However, the exact entropies and radii of newly formed planets due to these two modes of formation cannot, at present, be precisely predicted. It is possible that the distribution of properties of core-accretion-formed planets and the distribution of properties of disk-instability-formed planets overlap. We, therefore, introduce a broad range of 'warm-start' gas-giant planet models. Between the hottest and the coldest models that we consider, differences in radii, temperatures, luminosities, and spectra persist for only a few million to a few tens of millions of years for planets that are a few times Jupiter's mass or less. For planets that are {approx}five times Jupiter's mass or more, significant differences between hottest-start and coldest-start models persist for on the order of 100 Myr. We findmore » that out of the standard infrared bands (J, H, K, L', M, N) the K and H bands are the most diagnostic of the initial conditions. A hottest-start model can be from {approx}4.5 mag brighter (at Jupiter's mass) to {approx}9 mag brighter (at 10 times Jupiter's mass) than a coldest-start model in the first few million years. In more massive objects, these large differences in luminosity and spectrum persist for much longer than in less massive objects. Finally, we consider the influence of atmospheric conditions on spectra, and find that the presence or absence of clouds, and the metallicity of an atmosphere, can affect an object's apparent brightness in different bands by up to several magnitudes.« less

Abstract: Unlike most other planet-detection techniques, gravitational microlensing does not rely on detection of photons from either the host or the planet. Rather, planets are discovered by their gravitational perturbation of light from a more distant source. I review the fundamental concepts of microlensing planet searches and discuss their practical application. I show how the strengths and peculiarities of the method flow from the basic manner in which planets are discovered. In particular, microlensing is sensitive to very low-mass planets on wide orbits and free-floating planets, and can be used to search for planets orbiting host stars with a broad range of masses and Galactocentric distances. However, microlensing events are rare and cannot be predicted in advance, the majority of the host stars are extremely faint, and the planetary signals typically last less than a day. These strengths motivate microlensing searches as powerful, complementary probes of unexplored parameter space that have already provid...

Abstract: We present a statistical analysis that demonstrates that the overwhelming majority of Kepler candidate multiple transiting systems (multis) indeed represent true, physically associated transiting planets. Binary stars provide the primary source of false positives among Kepler planet candidates, implying that false positives should be nearly randomly distributed among Kepler targets. In contrast, true transiting planets would appear clustered around a smaller number of Kepler targets if detectable planets tend to come in systems and/or if the orbital planes of planets encircling the same star are correlated. There are more than one hundred times as many Kepler planet candidates in multi-candidate systems as would be predicted from a random distribution of candidates, implying that the vast majority are true planets. Most of these multis are multiple-planet systems orbiting the Kepler target star, but there are likely cases where (1) the planetary system orbits a fainter star, and the planets are thus significantly larger than has been estimated, or (2) the planets orbit different stars within a binary/multiple star system. We use the low overall false-positive rate among Kepler multis, together with analysis of Kepler spacecraft and ground-based data, to validate the closely packed Kepler-33 planetary system, which orbits a star that has evolved somewhat off of the main sequence. Kepler-33 hosts five transiting planets, with periods ranging from 5.67 to 41 days.

Abstract: Most planet pairs in the Kepler data that have measured transit time variations (TTVs) are near first-order mean-motion resonances. We derive analytical formulae for their TTV signals. We separate planet eccentricity into free and forced parts, where the forced part is purely due to the planets' proximity to resonance. This separation yields simple analytical formulae. The phase of the TTV depends sensitively on the presence of free eccentricity: if the free eccentricity vanishes, the TTV will be in phase with the longitude of conjunctions. This effect is easily detectable in current TTV data. The amplitude of the TTV depends on planet mass and free eccentricity, and it determines planet mass uniquely only when the free eccentricity is sufficiently small. We analyze the TTV signals of six short-period Kepler pairs. We find that three of these pairs (Kepler 18, 24, 25) have a TTV phase consistent with zero. The other three (Kepler 23, 28, 32) have small TTV phases, but ones that are distinctly non-zero. We deduce that the free eccentricities of the planets are small, 0.01, but not always vanishing. Furthermore, as a consequence of this, we deduce that the true masses of the planets are fairly accurately determined by the TTV amplitudes, within a factor of 2. The smallness of the free eccentricities suggests that the planets have experienced substantial dissipation. This is consistent with the hypothesis that the observed pile-up of Kepler pairs near mean-motion resonances is caused by resonant repulsion. But the fact that some of the planets have non-vanishing free eccentricity suggests that after resonant repulsion occurred there was a subsequent phase in the planets' evolution when their eccentricities were modestly excited, perhaps by interplanetary interactions.

Abstract: We determine the fraction of F, G, and K dwarfs in the solar neighborhood hosting hot Jupiters as measured by the California Planet Survey from the Lick and Keck planet searches. We find the rate to be 1.2% ± 0.38%, which is consistent with the rate reported by Mayor et al. from the HARPS and CORALIE radial velocity (RV) surveys. These numbers are more than double the rate reported by Howard et al. for Kepler stars and the rate of Gould et al. from the OGLE-III transit search; however, due to small number statistics these differences are of only marginal statistical significance. We explore some of the difficulties in estimating this rate from the existing RV data sets and comparing RV rates to rates from other techniques.

Abstract: The existence of gaseous giant planets whose orbits lie close to their host stars ('hot Jupiters') can largely be accounted for by planetary migration associated with viscous evolution of proto-planetary nebulae. Recently, observations of the Rossiter-McLaughlin effect during planetary transits have revealed that a considerable fraction of hot Jupiters are on orbits that are misaligned with respect to the spin axes of their host stars. This observation has cast doubt on the importance of disk-driven migration as a mechanism for producing hot Jupiters. Here I show that misaligned orbits can be a natural consequence of disk migration in binary systems whose orbital plane is uncorrelated with the spin axes of the individual stars. The gravitational torques arising from the dynamical evolution of idealized proto-planetary disks under perturbations from massive distant bodies act to misalign the orbital planes of the disks relative to the spin poles of their host stars. As a result, I suggest that in the absence of strong coupling between the angular momentum of the disk and that of the host star, or of sufficient dissipation that acts to realign the stellar spin axis and the planetary orbits, the fraction of planetary systems (including systems of 'hot Neptunes' and 'super-Earths') whose angular momentum vectors are misaligned with respect to their host stars will be commensurate with the rate of primordial stellar multiplicity.

Abstract: The past decade has seen a revolution in our understanding of protoplanetary disk evolution and planet formation in single-star systems. However, the majority of solar-type stars form in binary systems, so the impact of binary companions on protoplanetary disks is an important element in our understanding of planet formation. We have compiled a combined multiplicity/disk census of Taurus-Auriga, plus a restricted sample of close binaries in other regions, in order to explore the role of multiplicity in disk evolution. Our results imply that the tidal influence of a close (≾ 40 AU) binary companion significantly hastens the process of protoplanetary disk dispersal, as ~2/3 of all close binaries promptly disperse their disks within ≾1 Myr after formation. However, prompt disk dispersal only occurs for a small fraction of wide binaries and single stars, with ~80%-90% retaining their disks for at least ~2-3 Myr (but rarely for more than ~5 Myr). Our new constraints on the disk clearing timescale have significant implications for giant planet formation; most single stars have 3-5 Myr within which to form giant planets, whereas most close binary systems would have to form giant planets within ≾1 Myr. If core accretion is the primary mode for giant planet formation, then gas giants in close binaries should be rare. Conversely, since almost all single stars have a similar period of time within which to form gas giants, their relative rarity in radial velocity (RV) surveys indicates either that the giant planet formation timescale is very well matched to the disk dispersal timescale or that features beyond the disk lifetime set the likelihood of giant planet formation.

Abstract: We use models of thermal evolution and XUV-driven mass loss to explore the composition and history of low-mass low-density transiting planets. We investigate the Kepler-11 system in detail and provide estimates of both the current and past planetary compositions. We find that a H/He atmosphere on Kepler-11b is highly vulnerable to mass loss. By comparing to formation models, we show that in situ formation of the system is unlikely. Instead we propose that it is a water-rich system of sub-Neptunes that migrated from beyond the snow line. For the broader population of observed planets, we show that there is a threshold in bulk planet density and incident flux above which no low-mass transiting planets have been observed. We suggest that this threshold is due to the instability of H/He atmospheres to XUV-driven mass loss. Importantly, we find that this flux-density threshold is well reproduced by our thermal evolution/contraction models that incorporate a standard mass loss prescription. Treating the planets' contraction history is essential because the planets have significantly larger radii during the early era of high XUV fluxes. Over time low mass planets with H/He envelopes can be transformed into water-dominated worlds with steam atmospheres or rocky super-Earths. Finally, we use this threshold to provide likely minimum masses and radial velocity amplitudes for the general population of Kepler candidates. Likewise, we use this threshold to provide constraints on the maximum radii of low-mass planets found by radial velocity surveys.

Abstract: While conventional interior models for Jupiter and Saturn are based on the simplistic assumption of a solid core surrounded by a homogeneous gaseous envelope, we have derived new models with an inhomogeneous distribution of heavy elements within these planets. Such a compositional gradient hampers large-scale convection that turns into double-diffusive convection, yielding an inner thermal profile that departs from the traditionally assumed adiabatic interior and affecting these planets heat content and cooling history. To address this problem, we have developed an analytical approach to describe layered double-diffusive convection and apply this formalism to solar system gaseous giant planet interiors. These models satisfy all observational constraints and yield values for the metal enrichment of our gaseous giants that are up to 30% to 60% higher than previously thought. The models also constrain the size of the convective layers within the planets. Because the heavy elements tend to be redistributed within the gaseous envelope, the models predict smaller than usual central cores inside Saturn and Jupiter, with possibly no core for the latter. These models open a new window and raise new challenges to our understanding of the internal structure of giant (solar and extrasolar) planets, in particular on how to determine their heavy material content, a key diagnostic for planet formation theories.

Abstract: Context. The research of extrasolar planets has entered an era in which we characterize extrasolar planets. This has become possible with measurements of the radii of transiting planets and of the luminosity of planets observed by direct imaging. Meanwhile, the precision of radial velocity surveys makes it possible to discover not only giant planets but also very low-mass ones.Aims. Uniting all these different observational constraints into one coherent picture to better understand planet formation is an important and simultaneously difficult undertaking. One approach is to develop a theoretical model that can make testable predictions for all these observational techniques. Our goal is to have such a model and use it in population synthesis calculations.Methods. In a companion paper, we described how we have extended our formation model into a self-consistently coupled formation and evolution model. In this second paper, we first continue with the model description. We describe how we calculate the internal structure of the solid core of the planet and include radiogenic heating. We also introduce an upgrade of the protoplanetary disk model. Finally, we use the upgraded model in population synthesis calculations.Results. We present how the planetary mass-radius relationship of planets with primordial H2 /He envelopes forms and evolves in time. The basic shape of the mass-radius relationship can be understood from the core accretion model. Low-mass planets cannot bind massive envelopes, while super-critical cores necessarily trigger runway gas accretion, leading to “forbidden” zones in the M − R plane. For a given mass, there is a considerable diversity of radii, mainly due to different bulk compositions, reflecting different formation histories. We compare the synthetic M − R plane with the observed one, finding good agreement for a > 0.1 AU. The synthetic planetary radius distribution is characterized by a strong increase towards small R and a second, lower local maximum at about 1 R X . The increase towards small radii comes from the increase of the mass function towards low M . The second local maximum is due to the fact that radii are nearly independent of mass for giant planets. A comparison of the synthetic radius distribution with Kepler data shows good agreement for R ≳ 2 R ⊕ , but divergence for smaller radii. This indicates that for R ≳ 2 R ⊕ the radius distribution can be described with planets with primordial H2 /He atmospheres, while at smaller radii, planets of a different nature dominate. We predict that in the next few years, Kepler will find the second local maximum at about 1 R X . Conclusions. With the updated model, we can compute the most important quantities, like mass, semimajor axis, radius, and luminosity, which characterize an extrasolar planet self-consistently from its formation. The comparison of the radii of the synthetic planets with observations makes it possible to better constrain this formation process and to distinguish between fundamental types of planets.