Up to now,tremendous exoplanets have been discovered. However, only a few of them have been detcted 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-alpha by the escaping exoplanetary atmosphere for a sample of planets. Following are the main results.(1) Different types of planets have different 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 evaluate the heating efficiency and XUV absorption radius Rxuv for most of our sample. It is found that the heating efficiency is almost proportional to the product of Fxuv and the gravitational potential. Rxuv is higher when the planetary radius and mass are smaller.(3) The mass loss rates calculated by our hydrodynamic model are basically consistent with that of the energy-limited ones after correcting the thermal and kinetic energy of the escaping particles.(4) The deep Ly-alpha absorption is mainly distributed in the sample with high XUV 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.(6)The planetary systems with larger radii absorb more Ly-alpha radiation from the star.(7)Compared to the XUV flux, the XUV SEDs have more significant effectes on the Ly-alpha absorption.
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