15:00 〜 15:15
[PAE16-06] Effects of H2 pumping on hot Jupiter's atmospheric escape
キーワード：系外惑星、ホットジュピター、大気散逸
Observations have revealed atmospheric escape of hot Jupiters around various-type stars. Classically, extreme-ultraviolet (EUV; >13.6eV) radiation of the host stars is considered to be responsible for the atmospheric escape.
EUV radiation is particularly strong for low-mass young stars, while intermediate-mass stars are less luminous in EUV but have an intense far-ultraviolet (FUV; <13.6eV) radiation instead. Therefore, compared to EUV heating, FUV-associated heating can be relatively effective for hot jupiters around intermediate-mass stars. The Lyman-Werner photons can excite molecular hydrogen to upper vibrational states (so-called H2 pumping), and subsequent collisional de-excitation can result in substantial heating to the gas. Recent observations have discovered planets around A-stars, which have FUV luminosity about five orders of magnitude higher than the solar value. It is expected that H2 pumping is effective to drive atmospheric escape for such planets.
In this study, we investigate the heating effects on the dynamics of hot Jupiter's atmosphere, performing radiation hydrodynamic simulations with self-consistent thermochemistry. We found that H2 pumping can yield a mass-loss rate of ~ 1013 g/s around hot A-stars, which is orders of magnitude larger than typical mass-loss rates for EUV-driven escape (~1010 g/s). We discuss the effect of H2 pumping heating on the atmospheric escape process of hot Jupiters around various host stars.
EUV radiation is particularly strong for low-mass young stars, while intermediate-mass stars are less luminous in EUV but have an intense far-ultraviolet (FUV; <13.6eV) radiation instead. Therefore, compared to EUV heating, FUV-associated heating can be relatively effective for hot jupiters around intermediate-mass stars. The Lyman-Werner photons can excite molecular hydrogen to upper vibrational states (so-called H2 pumping), and subsequent collisional de-excitation can result in substantial heating to the gas. Recent observations have discovered planets around A-stars, which have FUV luminosity about five orders of magnitude higher than the solar value. It is expected that H2 pumping is effective to drive atmospheric escape for such planets.
In this study, we investigate the heating effects on the dynamics of hot Jupiter's atmosphere, performing radiation hydrodynamic simulations with self-consistent thermochemistry. We found that H2 pumping can yield a mass-loss rate of ~ 1013 g/s around hot A-stars, which is orders of magnitude larger than typical mass-loss rates for EUV-driven escape (~1010 g/s). We discuss the effect of H2 pumping heating on the atmospheric escape process of hot Jupiters around various host stars.