Aeronomical constraints to the minimum mass and maximum radius of hot low-mass planets
Aeronomical constraints to the minimum mass and maximum radius of hot low-mass planets
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热低质量行星的最小质量和最大半径的航空约束
DOI：
10.1051/0004-6361/201629716
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发表时间：
2016
期刊：
影响因子：
--
通讯作者：
S. Bauer
中科院分区：
文献类型：
--
作者：
L. Fossati;N. Erkaev;H. Lammer;P. Cubillos;P. Odert;I. Juvan;K. Kislyakova;M. Lendl;D. Kubyshkina;S. Bauer
刺激的发现，一些近在低密度行星，我们概括的牛仔裤逃逸参数考虑到流体动力学和罗氏瓣效应。我们还将$\Lambda$定义为根据观测到的行星半径和行星平衡温度质量并考虑原子氢计算的Jeans逃逸参数值，与大气温度分布无关。我们考虑5和10 $M_{\oplus}$行星的平衡温度为500和1000 K，早期的G-，K-和M-型恒星的轨道。假设有一个清晰的大气层，并通过比较从能量有限公式获得的逃逸率，该公式仅考虑了由高能恒星辐射吸收引起的加热，以及从流体动力学大气代码获得的逃逸率，该代码也考虑了热辐射加热，我们发现，其$\Lambda$小于15-35的行星处于“蒸发”状态，在那里逃逸是由大气热能和低行星引力驱动的。我们发现，大气的热（即T_{\rm eq}\gtrapprox $1000 K）低质量（$M_{\rm pl}\lessapprox $5 $M_{\oplus}$）行星与$\Lambda$ < 15-35收缩到更小的半径，使他们的$\Lambda$演变到高于15-35的值，因此在不到$\approx$5亿美元的蒸发制度。由于它们的洛希瓣半径很小，我们发现同样的结果也适用于热的（即T_{\rm eq}\gtrapprox $1000 K）更高质量（M_{\rm pl}\lessapprox $10 $M_{\oplus}$）的行星，当它们围绕M-矮星运行时，它们的质量小于15-35。因此，对于这个参数范围内以氢为主的古老行星，$\Lambda$应该是$\geq $15 -35，这对行星的最小质量和最大半径提供了强有力的约束，例如，可以用来预测气溶胶的存在和/或约束行星质量。
Stimulated by the discovery of a number of close-in low-density planets, we generalise the Jeans escape parameter taking hydrodynamic and Roche lobe effects into account. We furthermore define $\Lambda$ as the value of the Jeans escape parameter calculated at the observed planetary radius and mass for the planet's equilibrium temperature and considering atomic hydrogen, independently of the atmospheric temperature profile. We consider 5 and 10 $M_{\oplus}$ planets with an equilibrium temperature of 500 and 1000 K, orbiting early G-, K-, and M-type stars. Assuming a clear atmosphere and by comparing escape rates obtained from the energy-limited formula, which only accounts for the heating induced by the absorption of the high-energy stellar radiation, and from a hydrodynamic atmosphere code, which also accounts for the bolometric heating, we find that planets whose $\Lambda$ is smaller than 15-35 lie in the "boil-off" regime, where the escape is driven by the atmospheric thermal energy and low planetary gravity. We find that the atmosphere of hot (i.e. $T_{\rm eq}\gtrapprox$ 1000 K) low-mass ($M_{\rm pl}\lessapprox$ 5 $M_{\oplus}$) planets with $\Lambda$ < 15-35 shrinks to smaller radii so that their $\Lambda$ evolves to values higher than 15-35, hence out of the boil-off regime, in less than $\approx$500 Myr. Because of their small Roche lobe radius, we find the same result also for hot (i.e. $T_{\rm eq}\gtrapprox$ 1000 K) higher mass ($M_{\rm pl}\lessapprox$ 10 $M_{\oplus}$) planets with $\Lambda$ < 15-35, when they orbit M-dwarfs. For old, hydrogen-dominated planets in this range of parameters, $\Lambda$ should therefore be $\geq$15-35, which provides a strong constraint on the planetary minimum mass and maximum radius and can be used to predict the presence of aerosols and/or constrain planetary masses, for example.
开普勒数据集中的独立行星搜索 - II 开普勒 87 周围的极低密度超级地球质量行星
影响因子：
6.5
作者：
Dreizler;Stefan;Zechmeister;Mathias;Husser;Tim-Oliver
通讯作者：
Tim-Oliver