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Orbital Evolution of Close-in Super-Earths Driven by Atmospheric Escape by Fujita, Naho; Hori, Yasunori; Sasaki, Takanori is a scholarly article available to read on EtoBox.

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The increasing number of super-Earths close to their host stars revealed a scarcity of close-in small planets with 1.5-2.0$\,R_\oplus$ in the radius distribution of ${\it Kepler}$ planets. The atmospheric escape of super-Earths by photoevaporation can explain the origin of the observed "radius gap." Many theoretical studies considered the in-situ mass loss of a close-in planet. Planets that undergo the atmospheric escape, however, move outward due to the change in the orbital angular momentum of their star-planet systems. In this study, we calculate the orbital evolution of an evaporating super-Earth with a H$_2$/He atmosphere around FGKM-type stars under a stellar X-ray and extreme UV irradiation (XUV). The rate of increase in the orbital radius of an evaporating planet is approximately proportional to that of the atmospheric mass loss during a high stellar XUV phase. We show that super-Earths with a rocky core of $\lesssim$ 10$\,M_\oplus$ and a H$_2$/He atmosphere at $\lesssim$ 0.03-0.1$\,$au ($\lesssim$ 0.01-0.03$\,$au) around G-type stars (M-type stars) are prone to the outward migration driven by photoevaporation. Although the changes in the orbits of the planets would be smal

Author

Fujita, Naho; Hori, Yasunori; Sasaki, Takanori

Published

2022

Language

EN