[en] We report the discovery of the first hot Jupiter in the Hyades open cluster. HD 285507b orbits a V = 10.47 K4.5V dwarf (M _* = 0.734 M _☉; R _* = 0.656 R _☉) in a slightly eccentric (e=0.086_−0.019^+0.018) orbit with a period of 6.0881_−0.0018^+0.0019 days. The induced stellar radial velocity corresponds to a minimum companion mass of M _Psin i = 0.917 ± 0.033 M _Jup. Line bisector spans and stellar activity measures show no correlation with orbital phase, and the radial velocity amplitude is independent of wavelength, supporting the conclusion that the variations are caused by a planetary companion. Follow-up photometry indicates with high confidence that the planet does not transit. HD 285507b joins a small but growing list of planets in open clusters, and its existence lends support to a planet formation scenario in which a high stellar space density does not inhibit giant planet formation and migration. We calculate the circularization timescale for HD 285507b to be larger than the age of the Hyades, which may indicate that this planet's non-zero eccentricity is the result of migration via interactions with a third body. We also demonstrate a significant difference between the eccentricity distributions of hot Jupiters that have had time to tidally circularize and those that have not, which we interpret as evidence against Type II migration in the final stages of hot Jupiter formation. Finally, the dependence of the circularization timescale on the planetary tidal quality factor, Q _P, allows us to constrain the average value for hot Jupiters to be logQ_P=6.14_−0.25^+0.41.

[en] We report the discovery of two giant planets orbiting stars in Praesepe (also known as the Beehive Cluster). These are the first known hot Jupiters in an open cluster and the only planets known to orbit Sun-like, main-sequence stars in a cluster. The planets are detected from Doppler-shifted radial velocities; line bisector spans and activity indices show no correlation with orbital phase, confirming the variations are caused by planetary companions. Pr0201b orbits a V = 10.52 late F dwarf with a period of 4.4264 ± 0.0070 days and has a minimum mass of 0.540 ± 0.039 M_Jup, and Pr0211b orbits a V = 12.06 late G dwarf with a period of 2.1451 ± 0.0012 days and has a minimum mass of 1.844 ± 0.064 M_Jup. The detection of two planets among 53 single members surveyed establishes a lower limit of 3.8^+5.0_–2.4% on the hot Jupiter frequency in this metal-rich open cluster. Given the precisely known age of the cluster, this discovery also demonstrates that, in at least two cases, giant planet migration occurred within 600 Myr after formation. As we endeavor to learn more about the frequency and formation history of planets, environments with well-determined properties—such as open clusters like Praesepe—may provide essential clues to this end.

[en] The Kepler Mission relies on precise differential photometry to detect the 80 parts per million (ppm) signal from an Earth-Sun equivalent transit. Such precision requires superb instrument stability on timescales up to ∼2 days and systematic error removal to better than 20 ppm. To this end, the spacecraft and photometer underwent 67 days of commissioning, which included several data sets taken to characterize the photometer performance. Because Kepler has no shutter, we took a series of dark images prior to the dust cover ejection, from which we measured the bias levels, dark current, and read noise. These basic detector properties are essentially unchanged from ground-based tests, indicating that the photometer is working as expected. Several image artifacts have proven more complex than when observed during ground testing, as a result of their interactions with starlight and the greater thermal stability in flight, which causes the temperature-dependent artifact variations to be on the timescales of transits. Because of Kepler's unprecedented sensitivity and stability, we have also seen several unexpected systematics that affect photometric precision. We are using the first 43 days of science data to characterize these effects and to develop detection and mitigation methods that will be implemented in the calibration pipeline. Based on early testing, we expect to attain Kepler's planned photometric precision over 80%-90% of the field of view.

[en] We present 44 days of high duty cycle, ultra precise photometry of the 13th magnitude star Kepler-5 (KIC 8191672, T _eff= 6300 K, log g= 4.1), which exhibits periodic transits with a depth of 0.7%. Detailed modeling of the transit is consistent with a planetary companion with an orbital period of 3.548460 ± 0.000032 days and a radius of 1.431^+0.041_-0.052 R _J. Follow-up radial velocity measurements with the Keck HIRES spectrograph on nine separate nights demonstrate that the planet is more than twice as massive as Jupiter with a mass of 2.114^+0.056_-0.059 M _J and a mean density of 0.894 ± 0.079 g cm^-3.

[en] 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 (e.g., 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 1.°0-2.°2, for the packed systems of small planets probed by these observations.

[en] We report the discovery of KELT-2Ab, a hot Jupiter transiting the bright (V = 8.77) primary star of the HD 42176 binary system. The host is a slightly evolved late F-star likely in the very short-lived 'blue-hook' stage of evolution, with T_eff = 6148 ± 48 K, log g = 4.030^+0.015_–0.026 and [Fe/H] = 0.034 ± 0.78. The inferred stellar mass is M_* = 1.314^+0.063_–0.060 M_☉ and the star has a relatively large radius of R_* = 1.836^+0.066_–0.046 R_☉. The planet is a typical hot Jupiter with period 4.1137913 ± 0.00001 days and a mass of M_P = 1.524 ± 0.088 M_J and radius of R_P = 1.290^+0.064_–0.050 R_J. This is mildly inflated as compared to models of irradiated giant planets at the ∼4 Gyr age of the system. KELT-2A is the third brightest star with a transiting planet identified by ground-based transit surveys, and the ninth brightest star overall with a transiting planet. KELT-2Ab's mass and radius are unique among the subset of planets with V < 9 host stars, and therefore increases the diversity of bright benchmark systems. We also measure the relative motion of KELT-2A and -2B over a baseline of 38 years, robustly demonstrating for the first time that the stars are bound. This allows us to infer that KELT-2B is an early K dwarf. We hypothesize that through the eccentric Kozai mechanism KELT-2B may have emplaced KELT-2Ab in its current orbit. This scenario is potentially testable with Rossiter-McLaughlin measurements, which should have an amplitude of ∼44 m s^–1.

[en] Early time-series photometry from NASA's Kepler spacecraft has revealed a planet transiting the star we term Kepler-4, at R.A. = 19^h02^m27.^s68, δ = +50⁰08'08.''7. The planet has an orbital period of 3.213 days and shows transits with a relative depth of 0.87 x 10^-3 and a duration of about 3.95 hr. Radial velocity (RV) measurements from the Keck High Resolution Echelle Spectrometer show a reflex Doppler signal of 9.3^+1.1_-1.9 m s^-1, consistent with a low-eccentricity orbit with the phase expected from the transits. Various tests show no evidence for any companion star near enough to affect the light curve or the RVs for this system. From a transit-based estimate of the host star's mean density, combined with analysis of high-resolution spectra, we infer that the host star is near turnoff from the main sequence, with estimated mass and radius of 1.223^+0.053_-0.091 M _sun and 1.487^+0.071_-0.084 R _sun. We estimate the planet mass and radius to be {M _P, R _P} = {24.5 ± 3.8 M ₊, 3.99 ± 0.21 R ₊}. The planet's density is near 1.9 g cm^-3; it is thus slightly denser and more massive than Neptune, but about the same size.

[en] We present the discovery of KELT-1b, the first transiting low-mass companion from the wide-field Kilodegree Extremely Little Telescope-North (KELT-North) transit survey. A joint analysis of the spectroscopic, radial velocity, and photometric data indicates that the V = 10.7 primary is a mildly evolved mid-F star with T_eff = 6516 ± 49 K, log g 4.228^+0.014_–0.021, and [Fe/H] = 0.052 ± 0.079, with an inferred mass M_* = 1.335 ± 0.063 M_☉ and radius R_* 1.471^+0.045_–0.035 R_☉. The companion is a low-mass brown dwarf or a super-massive planet with mass M_P = 27.38 ± 0.93 M_Jup and radius R_P = 1.116^+0.038_–0.029 R_Jup. The companion is on a very short (∼29 hr) period circular orbit, with an ephemeris T_c (BJD_TDB) = 2455909.29280 ± 0.00023 and P = 1.217501 ± 0.000018 days. KELT-1b receives a large amount of stellar insolation, resulting in an estimated equilibrium temperature assuming zero albedo and perfect redistribution of T_eq = 2423⁺³⁴_–27 K. Comparison with standard evolutionary models suggests that the radius of KELT-1b is likely to be significantly inflated. Adaptive optics imaging reveals a candidate stellar companion to KELT-1 with a separation of 588 ± 1 mas, which is consistent with an M dwarf if it is at the same distance as the primary. Rossiter-McLaughlin measurements during transit imply a projected spin-orbit alignment angle λ = 2 ± 16 deg, consistent with a zero obliquity for KELT-1. Finally, the vsin I_* = 56 ± 2 km s^–1 of the primary is consistent at ∼2σ with tidal synchronization. Given the extreme parameters of the KELT-1 system, we expect it to provide an important testbed for theories of the emplacement and evolution of short-period companions, as well as theories of tidal dissipation and irradiated brown dwarf atmospheres.

[en] 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.

[en] A search of the time-series photometry from NASA's Kepler spacecraft reveals a transiting planet candidate orbiting the 11th magnitude G5 dwarf KIC 10593626 with a period of 290 days. The characteristics of the host star are well constrained by high-resolution spectroscopy combined with an asteroseismic analysis of the Kepler photometry, leading to an estimated mass and radius of 0.970 ± 0.060 M_☉ and 0.979 ± 0.020 R_☉. The depth of 492 ± 10 ppm for the three observed transits yields a radius of 2.38 ± 0.13 Re for the planet. The system passes a battery of tests for false positives, including reconnaissance spectroscopy, high-resolution imaging, and centroid motion. A full BLENDER analysis provides further validation of the planet interpretation by showing that contamination of the target by an eclipsing system would rarely mimic the observed shape of the transits. The final validation of the planet is provided by 16 radial velocities (RVs) obtained with the High Resolution Echelle Spectrometer on Keck I over a one-year span. Although the velocities do not lead to a reliable orbit and mass determination, they are able to constrain the mass to a 3σ upper limit of 124 M_⊕, safely in the regime of planetary masses, thus earning the designation Kepler-22b. The radiative equilibrium temperature is 262 K for a planet in Kepler-22b's orbit. Although there is no evidence that Kepler-22b is a rocky planet, it is the first confirmed planet with a measured radius to orbit in the habitable zone of any star other than the Sun.