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arXiv 1102.0547astro-ph.EP
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开普勒候选行星的Transit持续时间分布及其轨道偏心率的意义

The Distribution of Transit Durations for Kepler Planet Candidates and Implications for their Orbital Eccentricities

Althea V. Moorhead, Eric B. Ford, Robert C. Morehead, Jason Rowe, William J. Borucki, Natalie M. Batalha, Stephen T. Bryson, Douglas A. Caldwell, Daniel C. Fabr… 展开作者

Althea V. Moorhead, Eric B. Ford, Robert C. Morehead, Jason Rowe, William J. Borucki, Natalie M. Batalha, Stephen T. Bryson, Douglas A. Caldwell, Daniel C. Fabrycky, Thomas N. Gautier, David G. Koch, Matthew J. Holman, Jon M. Jenkins, Jie Li, Jack J. Lissauer, Philip Lucas, Geoffrey W. Marcy, Samuel N. Quinn, Elisa Quintana, Darin Ragozzine, Avi Shporer, Martin Still, Guillermo Torres

摘要:

多普勒行星搜索发现,巨大的行星遵循着各种轨道偏心率的轨道,彻底改变了行星形成的理论。美国宇航局开普勒任务发现了数百颗系外行星候选者,使天文学家能够描述小型系外行星的偏心率分布。测量单个行星的偏心率只有在适合于补充技术的有利情况下才是实际的(例如,径向速度,凌日时间变化,掩星测光)。然而,即使在没有单独的偏心率的情况下,也可以根据过境持续时间的分布(相对于圆形轨道的最大过境持续时间)来研究偏心率的分布。我们分析了开普勒行星候选者的过境持续时间分布。我们发现,对于T_eff > 5100 K的宿主星,由于宿主星密度的不确定性和可能的系统性,我们不能反演这一点来推断此时的偏心率分布。考虑到这一限制,我们将观测到的过境持续时间分布与模型进行比较,以排除极端分布。如果我们假设开普勒行星候选者的离心率为瑞利分布,那么对于T_eff < 5100 K的宿主星,我们发现平均离心率为0.1-0.25的最佳拟合。我们比较了开普勒行星候选者的不同子集的过境持续时间分布,并讨论了行星半径和多重性的初步趋势。将需要对大量主星进行高精度光谱跟踪观测,以确认哪些趋势是真实的,哪些是恒星半径的系统误差造成的。最后,我们确定行星候选人,必须是偏心或有一个显着低估的恒星半径。

英文摘要:

Doppler planet searches have discovered that giant planets follow orbits with a wide range of orbital eccentricities, revolutionizing theories of planet formation. The discovery of hundreds of exoplanet candidates by NASA's Kepler mission enables astronomers to characterize the eccentricity distribution of small exoplanets. Measuring the eccentricity of individual planets is only practical in favorable cases that are amenable to complementary techniques (e.g., radial velocities, transit timing variations, occultation photometry). Yet even in the absence of individual eccentricities, it is possible to study the distribution of eccentricities based on the distribution of transit durations (relative to the maximum transit duration for a circular orbit). We analyze the transit duration distribution of Kepler planet candidates. We find that for host stars with T_eff > 5100 K we cannot invert this to infer the eccentricity distribution at this time due to uncertainties and possible systematics in the host star densities. With this limitation in mind, we compare the observed transit duration distribution with models to rule out extreme distributions. If we assume a Rayleigh eccentricity distribution for Kepler planet candidates, then we find best-fits with a mean eccentricity of 0.1-0.25 for host stars with T_eff < 5100 K. We compare the transit duration distribution for different subsets of Kepler planet candidates and discuss tentative trends with planetary radius and multiplicity. High-precision spectroscopic follow-up observations for a large sample of host stars will be required to confirm which trends are real and which are the results of systematic errors in stellar radii. Finally, we identify planet candidates that must be eccentric or have a significantly underestimated stellar radius.

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