Driven by the high energy radiation of host stars, atmospheric escape is very important for planet evolution. We aim to study the mass-loss rate, the transition of escape mechanism, the comparison of X-ray and EUV heating, based on a one-dimensional hydrodynamic model which includes radiative transfer processes and photochemical reactions. As stellar XUV (extreme-ultraviolet and X-ray) emission varies with the stellar evolution, we use XSPEC to construct the XUV spectra at different age. We find that along with the increase of orbital distance, the mass-loss rates drops significantly, and when the stellar XUV flux is too small to preserve the hydrodynamic escape, it will turn to Jeans escape. This transition occurs in larger distance for younger and smaller planet. For young planets, hydrodynamic escape can occur in 1-2 AU. For very young close-in planets, the relation between mass-loss rates and stellar flux is not as significant as planets that are not close to their host stars, and the energy-limited equation can lead to large overestimate. In addition, X-ray radiation penetrates much deeper than EUV, and thus heating the lower boundary of planet atmosphere more effectively. In general, X-ray heating can contribute a large amount of mass loss rate, but except for close-in small planets orbit around very young stars, it is reasonable to ignore X-ray heating. As well as to stellar radiation, atmospheric escape is extremely sensitive to the gravitational potential. Planets have mass larger than 2.5MJup cannot preserve hydrodynamic escape with stellar age of 4.6 Gyr, even if the orbital distance is only 0.05 AU. We also present scaling laws for the heating efficiency and the expansion radius and the revised energy-limited escape equation can be used to derive mass-loss rates of hydrodynamic escape.
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