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Paper: Heating of the Upper Atmosphere of a Hot Jupiter for Various Spectral Energy Distributions of the Host Star
Volume: 496, Living Together: Planets, Host Stars and Binaries
Page: 343
Authors: Ionov, D. E.; Shematovich, V. I.; Bisikalo, D. V.
Abstract: We present the results of simulations of the heating processes in the upper atmosphere of the hot-Jupiter HD 209458b, taking into account mechanisms with suprathermal particles. The calculations are performed for various spectral energy distributions of the host star. The exoplanet HD 209458b is surrounded by a gaseous envelope that can be lost through the intensive outflow of the atmosphere gas. The rate of this outflow depends on the heating of the upper atmosphere by the stellar UV radiation in the range of 1–100 nm. We study the X-ray and UV heating rate separately in two bands: 1–10 nm (soft X-rays) and 10–100 nm (EUV radiation). We have found that the heating profile has two maxima. EUV radiation is absorbed at an altitude of 1.06 planetary radii. Soft X-rays are absorbed at an altitude of 1.02 radii. We have also found that the heating comes mainly from EUV radiation. The profiles of the heating efficiency for soft X-ray and EUV radiation have been calculated. The average heating efficiency is 0.12–0.20 for different ranges. For main-sequence stars the intensity at 1–10 nm varies over the course of the stellar evolution. For young stars the flux in this range can be greater by several orders of magnitude than the flux from stars that are several billion years old. Therefore, we have calculated the heating of the atmosphere for stellar XUV spectral distributions in which the intensity of the flux in the range of 1–10 nm exceeds the intensity of the solar flux over the same range by factors of 10 and 100. We have found that the growth of flux in the range 1–10 nm fundamentally changes the profile of the heating rate. However, the profile of the heating efficiency varies insignificantly.
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