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Results on the obliquity of exoplanet host stars—the angle between the stellar spin axis and the planetary orbital axis—provide important diagnostic information for theories describing planetary formation. Here we present the first application of asteroseismology to the problem of stellar obliquity determination in systems with transiting planets and Sun-like host stars.We consider two systems observed by theNASA Kepler mission which have multiple transiting small (super-Earth sized) planets: the previously reported Kepler-50 and a new system, Kepler-65, whose planets we validate in this paper. Both stars show rich spectra of solar-like oscillations. From the asteroseismic analysis we find that each host has its rotation axis nearly perpendicular to the line of sight with the sines of the angles constrained at the 1σ level to lie above 0.97 and 0.91, respectively. We use statistical arguments to show that coplanar orbits are favored in both systems, and that the orientations of the planetary orbits and the stellar rotation axis are correlated. [ABSTRACT FROM AUTHOR]

We report the discovery of HAT-P-17b,c, a multi-planet system with an inner transiting planet in a short-period, eccentric orbit and an outer planet in a 4.4 yr, nearly circular orbit. The inner planet, HAT-P-17b, transits the bright V = 10.54 early K dwarf star GSC 2717-00417, with an orbital period P = 10.338523 ± 0.000009 days, orbital eccentricity e = 0.342 ± 0.006, transit epoch Tc = 2454801.16943 ± 0.00020 (BJD: barycentric Julian dates throughout the paper are calculated from Coordinated Universal Time (UTC)), and transit duration 0.1690±0.0009 days. HAT-P-17b has a mass of 0.534±0.018 MJ and radius of 1.010±0.029 RJ yielding a mean density of 0.64 ± 0.05 g cm-3. This planet has a relatively low equilibrium temperature in the range 780-927 K, making it an attractive target for follow-up spectroscopic studies. The outer planet, HAT-P-17c, has a significantly +0.18 longer orbital period P2 = 1610 ± 20 days and a minimum mass m2 sin i2 = 1.31-0.15+0.18 MJ. The orbital inclination of HAT-P-17c is unknown as transits have not been observed and may not be present. The host star has a mass of 0.86 ± 0.04 Mʘ, radius of 0.84 ± 0.02 Rʘ, effective temperature 5246 ± 80 K, and metallicity [Fe/H] = 0.00 ± 0.08. HAT-P-17 is the second multi-planet system detected from ground-based transit surveys. [ABSTRACT FROM AUTHOR]

We report the discovery of HAT-P-25b, a transiting extrasolar planet orbiting the V = 13.19 G5 dwarf star GSC 1788-01237, with a period P = 3.652836 ± 0.000019 days, transit epoch Tc = 2455176.85173 ± 0.00047 (BJD— barycentric Julian dates throughout the paper are calculated from Coordinated Universal Time, UTC), and transit duration 0,1174 ± 0.0017 days. The host star has a mass of 1.01 ± 0.03 Mʘ, radius of 0.96 Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. Rʘ, effective temperature 5500 ± 80 K, and metallicity [Fe/H] = +0.31 ± 0.08. The planetary companion has a mass of 0.567 ± 0.022 Mj and radius of 1.190 Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. Rj yielding a mean density of 0.42 ± 0.07 gcm-3. [ABSTRACT FROM AUTHOR]

We report the discovery of four relatively massive (2-7 MJ) transiting extrasolar planets. HAT-P-20b orbits the moderately bright V = 11.339 K3 dwarf star GSC 1910-00239 on a circular orbit, with a period P = 2.875317 ± 0.000004 days, transit epoch Tc = 2455080.92661 ± 0.00021 (BJDUTC), and transit duration 0.0770 ± 0.0008 days. The host star has a mass of 0.76 ± 0.03 M⊙, radius of 0.69 ± 0.02 R⊙, effective temperature 4595 ± 80 K, and metallicity [Fe/H] = +0.35 ± 0.08. The planetary companion has a mass of 7.246 ± 0.187 MJ and a radius of 0.867 ± 0.033 RJ yielding a mean density of 13.78 ± 1.50 g cm-3. HAT-P-21b orbits the V = 11.685 G3 dwarf star GSC 3013-01229 on an eccentric (e = 0.228 ± 0.016) orbit, with a period P = 4.124481 ± 0.000007 days, transit epoch Tc = 2454996.41312 ± 0.00069, and transit duration 0.1530 ± 0.0027 days. The host star has a mass of 0.95 ± 0.04 M⊙, radius of 1.10 ± 0.08 R⊙, effective temperature 5588 ± 80 K, and metallicity [Fe/H] = +0.01 ± 0.08. The planetary companion has a mass of 4.063 ± 0.161 MJ and a radius of 1.024 ± 0.092 RJ yielding a mean density of Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. HAT-P-21b is a borderline object between the pM and pL class planets, and the transits occur near apastron. HAT-P-22b orbits the bright V = 9.732 G5 dwarf star HD 233731 on a circular orbit, with a period P = 3.212220 ± 0.000009 days, transit epoch Tc = 2454930.22001 ± 0.00025, and transit duration 0.1196 ± 0.0014 days. The host star has a mass of 0.92 ±0.03 M⊙, radius of 1.04 ± 0.04 R⊙, effective temperature 5302 ± 80 K, and metallicity [Fe/H] = +0.24 ± 0.08. The planet has a mass of 2.147 ± 0.061 MJ and a compact radius of 1.080 ± 0.058 RJ yielding a mean density of Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. The host star also harbors an M-dwarf companion at a wide separation. Finally, HAT-P-23b orbits the V = 12.432 G0 dwarf star GSC 1632-01396 on a close to circular orbit, with a period P = 1.212884 ± 0.000002 days, transit epoch Tc = 2454852.26464 ± 0.00018, and transit duration 0.0908 ± 0.0007 days. The host star has a mass of 1.13 ± 0.04 M⊙, radius of 1.20 ± 0.07 R⊙, effective temperature 5905 ± 80 K, and metallicity [Fe/H] = +0.15 ± 0.04. The planetary companion has a mass of 2.090 ± 0.111 MJ and a radius of 1.368 ± 0.090 RJ yielding a mean density of 1.01 ± 0.18 g cm-3. HAT-P-23b is an inflated and massive hot Jupiter on a very short period orbit, and has one of the shortest characteristic infall times (Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed Myr) before it gets engulfed by the star. [ABSTRACT FROM AUTHOR]

We report the discovery of two exoplanets transiting high-jitter stars. HAT-P-32b orbits the bright V = 11.289 late-F-early-G dwarf star GSC 3281-00800, with a period P = 2.150008 ± 0.000001 d. The stellar and planetary masses and radii depend on the eccentricity of the system, which is poorly constrained due to the high-velocity jitter (~80 m s-1). Assuming a circular orbit, the star has a mass of 1.16 ± 0.04 MJ and radius of 1.22 ± 0.02 R⊙, while the planet has a mass of 0.860 ± 0.164 MJ and a radius of 1.789 ± 0.025 RJ. The second planet, HAT-P-33b, orbits the bright V = 11.188 late-F dwarf star GSC 2461-00988, with a period P = 3.474474 ± 0.000001 d. As for HAT-P-32, the stellar and planetary masses and radii of HAT-P-33 depend on the eccentricity, which is poorly constrained due to the high jitter (~50m s-1). In this case, spectral line bisector spans (BSs) are significantly anti-correlated with the radial velocity residuals, and we are able to use this correlation to reduce the residual rms to ~35 m s-1. We find that the star has a mass of 1.38 ± 0.04 M⊙ and a radius of 1.64 ± 0.03 R⊙ while the planet has a mass of 0.762 ± 0.101 MJ and a radius of 1.686 ± 0.045 RJ for an assumed circular orbit. Due to the large BS variations exhibited by both stars we rely on detailed modeling of the photometric light curves to rule out blend scenarios. Both planets are among the largest radii transiting planets discovered to date. [ABSTRACT FROM AUTHOR]

We report the discovery of HAT-P-30b, a transiting exoplanet orbiting the V = 10.419 dwarf star GSC 0208-00722. The planet has a period P = 2.8 10595 ± 0.000005 days, transit epoch Tc = 2455456.46561 ± 0.00037 (BJD), and transit duration 0.0887 ± 0.0015 days. The host star has a mass of 1.24 ± 0.04 M..., radius of 1.21 ± 0.05 R..., effective temperature of 6304±88 K, and metallicity [Fe/H] = +0.13 ± 0.08. The planetary companion has a mass of 0.711 ± 0.028 MJ and radius of 1.340±0.065 RJ yielding a mean density of 0.37 ± 0.05 g cm-3. We also present radial velocity measurements that were obtained throughout a transit that exhibit the Rossiter-McLaughlin effect. By modeling this effect, we measure an angle of λ = 73°5 ± 9°0 between the sky projections of the planet's orbit normal and the star's spin axis. HAT-P-30b represents another example of a close-in planet on a highly tilted orbit, and conforms to the previously noted pattern that tilted orbits are more common around stars with Teff* ≳ 6250 K. [ABSTRACT FROM AUTHOR]

We report the discovery of HAT-P-27b, an exoplanet transiting the moderately bright G8 dwarf star GSC 0333-0035 1 (V = 12.214). The orbital period is 3.039586 ± 0.000012 days, the reference epoch of transit is 2455186.01879 ± 0.00054 (BJD), and the transit duration is 0.0705 ± 0.0019 days. The host star with its effective temperature 5300± 90 K is somewhat cooler than the Sun and is more metal-rich with a metallicity of +0.29±0.10. Its mass is 0.94 ± 0.04 M⊙ and radius is 0.90+0.05-0.04R⊙. For the planetary companion we determine a mass of 0.660 ± 0.033 MJ and radius of 1.038+0.077-0.058 RJ. For the 30 known transiting exoplanets between 0.3 MJ and 0.8 MJ, a negative correlation between host star metallicity and planetary radius and an additional dependence of planetary radius on equilibrium temperature are confirmed at a high level of statistical significance. [ABSTRACT FROM AUTHOR]

We present the discovery of two transiting exoplanets. HAT-P-28b orbits a V = 13.03 G3 dwarf star with a period P = 3.2572 days and has a mass of 0.63 ± 0.04 MJ and a radius of 1.21+0.11 RJ yielding a mean density of 0.44 ± 0.09 g cm-3. HAT-P-29b orbits a V = 11.90 F8 dwarf star with a period P = 5.7232 days and has a mass of 0.78+0.08-0.04 MJ and a radius of 1.1+0.14-0.08 RJ yielding a mean density of 0.71 ± 0.18 g cm-3. We discuss the properties of these planets in the context of other known transiting planets. [ABSTRACT FROM AUTHOR]

Rotation is expected to have an important influence on the structure and the evolution of stars. However, the mechanisms of angular momentum transport in stars remain theoretically uncertain and very complex to take into account in stellar models. To achieve a better understanding of these processes, we desperately need observational constraints on the internal rotation of stars, which until very recently was restricted to the Sun. In this paper, we report the detection of mixed modes—i.e., modes that behave both as g modes in the core and as p modes in the envelope—in the spectrum of the early red giant KIC 7341231, which was observed during one year with the Kepler spacecraft. By performing an analysis of the oscillation spectrum of the star, we show that its non-radial modes are clearly split by stellar rotation and we are able to determine precisely the rotational splittings of 18 modes. We then find a stellar model that reproduces very well the observed atmospheric and seismic properties of the star. We use this model to perform inversions of the internal rotation profile of the star, which enables us to show that the core of the star is rotating at least five times faster than the envelope. This will shed new light on the processes of transport of angular momentum in stars. In particular, this result can be used to place constraints on the angular momentum coupling between the core and the envelope of early red giants, which could help us discriminate between the theories that have been proposed over the last few decades. [ABSTRACT FROM AUTHOR]

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 FROM AUTHOR]

We study stars in the Lick planetary survey for correlations between simultaneous measurements of high-precision radial velocities vr and magnetic activity (as measured in an SIR emission index from Ca ii lambda8662). We find significant correlations in approximately 30% of the stars. After removing linear trends between SIR and vr, we find that the dispersion in vr in these stars is decreased by an average of 17%, or approximately 45% of the dispersion above the measurement noise. F stars and less active stars with variable Ca ii H and K lines are the most successfully corrected. The magnitude of the slope of the SIR versus vr relations increases proportional to vsini and (excepting M dwarfs) tends to decrease with decreasing Teff. We argue that the main cause of these effects is modification of the mean line bisector shape brought on by long-term, magnetic activity-induced changes in the surface brightness and convective patterns. The correlations can be used to partially correct vr data for the effects of long-term activity variations, potentially permitting study of planets around some (higher mass) younger stars and planets producing smaller stellar reflex velocities.