Kepler-62: A Five-Planet System with Planets of 1.4 and 1.6 Earth Radii in the Habitable Zone

We present the detection of five planets—Kepler-62b, c, d, e, and f—of size 1.31, 0.54, 1.95, 1.61 and 1.41 Earth radii (R[subscript ⊕]), orbiting a K2V star at periods of 5.7, 12.4, 18.2, 122.4, and 267.3 days, respectively. The outermost planets, Kepler-62e and -62f, are super–Earth-size (1.25 R[subscript ⊕] < planet radius ≤ 2.0 R[subscript ⊕]) planets in the habitable zone of their host star, respectively receiving 1.2 ± 0.2 times and 0.41 ± 0.05 times the solar flux at Earth’s orbit. Theoretical models of Kepler-62e and -62f for a stellar age of ~7 billion years suggest that both planets could be solid, either with a rocky composition or composed of mostly solid water in their bulk.United States. National Aeronautics and Space Administration (Kepler Participating Scientist Program Grant NNX12AC76G

Starspots and spin-orbit alignment for Kepler cool host stars

The angle between the spin axis of the host star and the orbit of its planets (i.e., the stellar obliquity) is precious information about the formation and evolution of exoplanetary systems. Measurements of the Rossiter-McLaughlin effect revealed that many stars that host a hot-Jupiter have high obliquities, suggesting that hot-Jupiter formation involves excitation of orbital inclinations. In this contribution we show how the passage of the planet over starspots can be used to measure the obliquity of exoplanetary systems. This technique is used to obtain - for the first time - the obliquity of a system with several planets that lie in a disk, Kepler-30, with the result that the star has an obliquity smaller than 10 degrees. The implications for the formation of exoplanetary systems, in particular the hot-Jupiter population, are also discussed.Comment: To appear in special edition of AN, proceedings of the Cool Stars 17 conference, Barcelona June 201

Stellar Spin-Orbit Misalignment in a Multiplanet System

Stars hosting hot Jupiters are often observed to have high obliquities, whereas stars with multiple coplanar planets have been seen to have low obliquities. This has been interpreted as evidence that hot-Jupiter formation is linked to dynamical disruption, as opposed to planet migration through a protoplanetary disk. We used asteroseismology to measure a large obliquity for Kepler-56, a red giant star hosting two transiting coplanar planets. These observations show that spin-orbit misalignments are not confined to hot-Jupiter systems. Misalignments in a broader class of systems had been predicted as a consequence of torques from wide-orbiting companions, and indeed radial velocity measurements revealed a third companion in a wide orbit in the Kepler-56 system.United States. National Aeronautics and Space Administration (Science Mission Directorate)United States. National Aeronautics and Space Administration (NASA Postdoctoral Program at Ames Research Center)National Science Foundation (U.S.) (NSF Graduate Research Fellowship)National Science Foundation (U.S.) (NSF Graduate Research Fellowship, grant DGE1144469)Netherlands Organization for Scientific ResearchBelgian Federal Science Policy Office (BELSPO, contract PRODEX COROT)United States. National Aeronautics and Space Administration (NASA Kepler Participating Scientist program)National Science Foundation (U.S.) (NSF grant AST-1105930)David & Lucile Packard FoundationAlfred P. Sloan FoundationHarvard-Smithsonian Center for Astrophysics (Hubble Fellow

The Transit Light Curve project. XIV. Confirmation of Anomalous Radii for the Exoplanets TrES-4b, HAT-P-3b, and WASP-12b

We present transit photometry of three exoplanets, TrES-4b, HAT-P-3b, and WASP-12b, allowing for refined estimates of the systems' parameters. TrES-4b and WASP-12b were confirmed to be "bloated" planets, with radii of 1.706 +/- 0.056 R_Jup and 1.736 +/- 0.092 R_Jup, respectively. These planets are too large to be explained with standard models of gas giant planets. In contrast, HAT-P-3b has a radius of 0.827 +/- 0.055 R_Jup, smaller than a pure hydrogen-helium planet and indicative of a highly metal-enriched composition. Analyses of the transit timings revealed no significant departures from strict periodicity. For TrES-4, our relatively recent observations allow for improvement in the orbital ephemerides, which is useful for planning future observations.Comment: AJ, in press [11 pages]; corrected error in distance to WASP-1

Measurements of Stellar Inclinations for Kepler Planet Candidates II: Candidate Spin-Orbit Misalignments in Single and Multiple-Transiting Systems

We present a test for spin-orbit alignment for the host stars of 25 candidate planetary systems detected by the {\it Kepler} spacecraft. The inclination angle of each star's rotation axis was estimated from its rotation period, rotational line broadening, and radius. The rotation periods were determined using the {\it Kepler} photometric time series. The rotational line broadening was determined from high-resolution optical spectra with Subaru/HDS. Those same spectra were used to determine the star's photospheric parameters (effective temperature, surface gravity, metallicity) which were then interpreted with stellar-evolutionary models to determine stellar radii. We combine the new sample with the 7 stars from our previous work on this subject, finding that the stars show a statistical tendency to have inclinations near 90$^\circ$, in alignment with the planetary orbits. Possible spin-orbit misalignments are seen in several systems, including three multiple-planet systems (KOI-304, 988, 2261). Ideally these systems should be scrutinized with complementary techniques---such as the Rossiter-McLaughlin effect, starspot-crossing anomalies or asteroseismology---but the measurements will be difficult owing to the relatively faint apparent magnitudes and small transit signals in these systems.Comment: 11 pages, 9 figures, accepted for publication in Ap

Transits and Occultations of an Earth-Sized Planet in an 8.5-Hour Orbit

We report the discovery of an Earth-sized planet ($1.16\pm 0.19 R_\oplus$) in an 8.5-hour orbit around a late G-type star (KIC 8435766, Kepler-78). The object was identified in a search for short-period planets in the {\it Kepler} database and confirmed to be a transiting planet (as opposed to an eclipsing stellar system) through the absence of ellipsoidal light variations or substantial radial-velocity variations. The unusually short orbital period and the relative brightness of the host star ($m_{\rm Kep}$ = 11.5) enable robust detections of the changing illumination of the visible hemisphere of the planet, as well as the occultations of the planet by the star. We interpret these signals as representing a combination of reflected and reprocessed light, with the highest planet dayside temperature in the range of 2300 K to 3100 K. Follow-up spectroscopy combined with finer sampling photometric observations will further pin down the system parameters and may even yield the mass of the planet.Comment: Accepted for publication, ApJ, 10 pages and 6 figure

The Roche Limit for Close-orbiting Planets: Minimum Density, Composition Constraints, and Application to the 4.2 hr Planet KOI 1843.03

The requirement that a planet must orbit outside of its Roche limit gives a lower limit on the planet's mean density. The minimum density depends almost entirely on the orbital period and is immune to systematic errors in the stellar properties. We consider the implications of this density constraint for the newly identified class of small planets with periods shorter than half a day. When the planet's radius is accurately known, this lower limit to the density can be used to restrict the possible combinations of iron and rock within the planet. Applied to KOI 1843.03, a 0.6 R⊕ planet with the shortest known orbital period of 4.245 hr, the planet's mean density must be ≳7 g cm^(–3). By modeling the planetary interior subject to this constraint, we find that the composition of the planet must be mostly iron, with at most a modest fraction of silicates (≾30% by mass)