The 55 Cancri system reassessed
The 55 Cancri system reassessed
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DOI：
10.1051/0004-6361/201833154
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发表时间：
2018-10-30
影响因子：
6.5
通讯作者：
Ehrenreich, D.
中科院分区：
文献类型：
--
作者：
Bourrier, V.;Dumusque, X.;Ehrenreich, D.
围绕一颗明亮的附近星星运行的55 CNC系统提供了一个难得的机会来研究一个多行星系统，该系统具有广泛的行星质量和轨道距离。利用20年的光度学和光谱学数据，我们测量了主星星的自转和它的类太阳磁周期。在我们对系统的测速分析中考虑到这个周期，我们可以修改最外面的巨行星及其四个行星同伴的属性。最内侧的行星55 Cnc e是一个异常接近的超级地球，其过境允许进行详细的后续研究。最近的观测支持存在大量的大气层，但其组成和行星的性质仍然未知。我们将我们推导出的行星质量（M-p = 8.0 +/- 0.3 M-Earth）与HST/STIS观测得出的光学半径的精确测量（R-p = 1.88 +/- 0.03 REarth在530-750 nm范围内）相结合，以修正55 Cnc e的密度（rho = 6.7 +/- 0.4 g cm（3））。基于这些修改后的属性，我们已经表征了可能的内部55 CNC E使用广义贝叶斯模型。我们确认，这颗行星很可能被一个重量级的大气层所包围，贡献了行星半径的几分之一。虽然我们不能排除大气层下存在水层的可能性，但考虑到对整个光谱和强烈辐射的观测，这种情况不太可能发生。需要在不同的时间尺度上对该系统进行测光和光谱学的后续观测，以进一步研究这一标志性超级地球的性质和起源。
Orbiting a bright, nearby star the 55 Cnc system offers a rare opportunity to study a multiplanet system that has a wide range of planetary masses and orbital distances. Using two decades of photometry and spectroscopy data, we have measured the rotation of the host star and its solar-like magnetic cycle. Accounting for this cycle in our velocimetric analysis of the system allows us to revise the properties of the outermost giant planet and its four planetary companions. The innermost planet 55 Cnc e is an unusually close-in super-Earth, whose transits have allowed for detailed follow-up studies. Recent observations favor the presence of a substantial atmosphere yet its composition, and the nature of the planet, remain unknown. We combined our derived planet mass (M-p = 8.0 +/- 0.3 M-Earth) with refined measurement of its optical radius derived from HST/STIS observations (R-p = 1.88 +/- 0.03 REarth over 530-750 nm) to revise the density of 55 Cnc e (rho = 6.7 +/- 0.4 g cm(3)). Based on these revised properties we have characterized possible interiors of 55 Cnc e using a generalized Bayesian model. We confirm that the planet is likely surrounded by a heavyweight atmosphere, contributing a few percents of the planet radius. While we cannot exclude the presence of a water layer underneath the atmosphere, this scenario is unlikely given the observations of the planet across the entire spectrum and its strong irradiation. Follow-up observations of the system in photometry and in spectroscopy over different time-scales are needed to further investigate the nature and origin of this iconic super-Earth.