Kepler-77b: a very low albedo, Saturn-mass transiting planet around a metal-rich solar-like star
Kepler-77b: a very low albedo, Saturn-mass transiting planet around a metal-rich solar-like star
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DOI：
10.1051/0004-6361/201321901
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发表时间：
2013-05
影响因子：
6.5
通讯作者：
D. Gandolfi;H. Parviainen;M. Fridlund;A. Hatzes;H. Deeg;A. Frasca;Antonino Francesco Lanza;P. Moroni;E. Tognelli;A. McQuillan;S. Aigrain;R. Alonso;V. Antoci;J. Cabrera;L. Carone;S. Csizmadia;A. A. Djupvik-A.;E. Guenther;J. Jessen-Hansen;A. Ofir;J. Telting
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文献类型：
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作者：
D. Gandolfi;H. Parviainen;M. Fridlund;A. Hatzes;H. Deeg;A. Frasca;Antonino Francesco Lanza;P. Moroni;E. Tognelli;A. McQuillan;S. Aigrain;R. Alonso;V. Antoci;J. Cabrera;L. Carone;S. Csizmadia;A. A. Djupvik-A.;E. Guenther;J. Jessen-Hansen;A. Ofir;J. Telting
我们报道了开普勒-77b(别名KOI-127.01)的发现。开普勒-77b是一颗土星质量的行星，绕着一颗富含金属的类日恒星运行3.6d的轨道。我们结合了公开可用的开普勒光度测量(1季度−13)和来自麦克唐纳的桑迪福德的高分辨率光谱和FIES的NOT光谱仪。我们通过对光度测量和径向速度测量同时进行联合拟合，得到了系统参数。我们的分析是基于贝叶斯方法，并通过使用马尔可夫链蒙特卡罗模拟对参数后验分布进行采样来进行的。开普勒-77b是一颗中等膨胀的行星，质量MP=0.430±0.032 MJup，半径Rp=0.960±0.016 RJ，体积密度ρp=0.603±0.055 Gcm−3。它的轨道是一颗缓慢旋转(Prot=36±6天)的G5V星，M�=0.95±0.0 4M�，R�=0.99±0.0 2R�，Tef=5 5 2 0±6 0K，[M/H]=0.2 0±0.0 5dex，年龄为7.5±2.0Gyr。缺乏深度高于∼10ppm的可探测行星掩星意味着行星的几何反照率和键反照率分别为Ag≤0.087±0.008和AB≤0.058±0.006，使开普勒-77b成为迄今反照率最低的气态巨行星之一。我们在∼0.5min的水平上既没有发现额外的行星凌日信号，也没有发现凌日时间的变化，这与近距离气态巨行星似乎属于单行星系统的趋势一致。开普勒在近1.2年的短节奏模式下观测到的106次凌日，没有显示出该行星在恒星黑子前面经过的迹象。我们探索了没有可探测到的黑子交叉事件对恒星自旋轴的倾角、天空投射的自旋轨道倾角和磁活动区的纬度的影响。
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 solarlike star.Wecombined the publicly availableKepler photometry (quarters 1−13) withhigh-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 Mp = 0.430 ± 0.032 MJup, a radius of Rp = 0.960 ± 0.016 RJup, and a bulk density of ρp = 0.603 ± 0.055 gcm −3 . It orbits a slowly rotating (Prot = 36 ±6 days) G5V star with M� = 0.95 ±0.04 M� , R� = 0.99 ±0.02 R� , Teff = 5520 ±60 K, [M/H] = 0.20 ±0.05dex, that has an age of 7.5 ± 2.0 Gyr. The lack of detectable planetary occultation with a depth higher than ∼10ppm implies a planet geometric and Bond albedo of Ag ≤ 0.087 ± 0.008 and AB ≤ 0.058 ± 0.006, respectively, placing Kepler-77b among the gas-giant planets with the lowest albedo known so far. Wefound neither additional planetary transit signals nor transit-timing variations at a level of ∼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.