| Up to now,tremendous exoplanets have been discovered.However,only a few of them have been detected experiencing atmospheric escape,and the escaping signals are not fully studied.In this paper,we evaluate the exoplanets' mass loss rates and the absorption of stellar Ly? by the escaping exoplanetary atmosphere for a sample of planets.We find:(1)Different types of planets have different of mass loss rates even if they receive the same amount of XUV radiation(Fxuv).For a given Fxuv,the mass loss rate for a Jupiter-like planet is about 100 times that of an Earth-like planet.(2)We calculate the heating efficiency ? and the XUV absorption radius Rxuv for most planets of our sample.It is found that the heating efficiency is almost proportional to the product of Fxuv and the gravitational potential(i.e.,log(Fxuv*G*Mp/Rp)).Rxuv is higher when the radius and mass of the planet are smaller.(3)After correcting for the kinetic and thermal energy of the escaping particles,the mass loss rates calculated by our hydrodynamic model are basically consistent with that predicted by the energy-limit equation.(4)The deep Ly? absorption is mainly distributed in the sample with high XUV radiation flux and low planetary mean density,and vice versa.(5)Different absorption levels are correlated with the mass loss rates of the planets.The greater the mass loss rates,the deeper the absorption will be.When the mass loss rates are 1011g/s or higher,the absorption depth will become significant.(6)The planetary systems with larger radii absorb more Ly? radiation from the host stars.Most of the hot-Jupiters and hot-Saturns in the sample have strong absorption of Ly?.Most hot Neptune and Earth-like planets have relatively weak Ly? absorption.(7)We analyzed the effects of different XUV integral flux(Fxuv)and XUV energy spectrum distribution(XUV SEDs)on Ly? absorption depth,and found that XUV SEDs had more significant effects on the absorption depth than Fxuv. |
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