We report the discovery of Kepler-77b (alias KOI-127.01), a Saturn-mass transiting planet in a 3.6-day orbit around a metal-rich solar-like star. We combined the publicly available Kepler photometry (quarters 1-13) with high-resolution spectroscopy from the Sandiford at McDonald and FIES at NOT spectrographs. We derived the system parameters via a simultaneous joint fit to the photometric and radial velocity measurements. Our analysis is based on the Bayesian approach and is carried out by sampling the parameter posterior distributions using a Markov chain Monte Carlo simulation. Kepler-77b is a moderately inflated planet with a mass of M-p = 0.430 +/- 0.032 M-Jup, a radius of R-p = 0.960 +/- 0.016 R-Jup, and a bulk density of rho(p) = 0.603 +/- 0.055 g cm(-3). It orbits a slowly rotating (P-rot = 36 +/- 6 days) G5V star with M-star = 0.95 +/- 0.04 M-circle dot, R-star = 0.99 +/- 0.02 R-circle dot, T-eff = 5520 +/- 60 K, [M/H] = 0.20 +/- 0.05 dex, that has an age of 7.5 +/- 2.0 Gyr. The lack of detectable planetary occultation with a depth higher than similar to 10 ppm implies a planet geometric and Bond albedo of A(g) <= 0.087 +/- 0.008 and A(B) <= 0.058 +/- 0.006, respectively, placing Kepler-77b among the gas-giant planets with the lowest albedo known so far. We found neither additional planetary transit signals nor transit-timing variations at a level of similar to 0.5 min, in accordance with the trend that close-in gas giant planets seem to belong to single-planet systems. The 106 transits observed in short-cadence mode by Kepler for nearly 1.2 years show no detectable signatures of the planet's passage in front of starspots. We explored the implications of the absence of detectable spot-crossing events for the inclination of the stellar spin-axis, the sky-projected spin-orbit obliquity, and the latitude of magnetically active regions.
|Autori:||D. Gandolfi;H. Parviainen;M. Fridlund;A. P. Hatzes;H. J. Deeg;A. Frasca;A. F. Lanza;P. G. Prada Moroni;E. Tognelli;A. McQuillan;S. Aigrain;R. Alonso;V. Antoci;J. Cabrera;L. Carone;S. Csizmadia;A. A. Djupvik;E. W. Guenther;J. Jessen-Hansen;A. Ofir;J. Telting|
|Titolo:||Kepler-77b: a very low albedo, Saturn-mass transiting planet around a metal-rich solar-like star|
|Anno del prodotto:||2013|
|Digital Object Identifier (DOI):||10.1051/0004-6361/201321901|
|Appare nelle tipologie:||1.1 Articolo in rivista|