Presentation #111.03 in the session “Extrasolar Planets: Atmospheric Models”.
The heating by photo-ionization in the thermosphere of short-period exoplanets can drive hydrodynamic escape, which is key to understanding the evolution of the planet atmosphere and explaining the atmospheric measurements. Besides powering the atmosphere escape, the energy deposited by EUV photons from the host star can also be radiated away through collisional excited atomic spectral lines, leading the mass loss rate to fall significantly below the energy limit. Recent observations have detected atomic Mg and Fe features in the transmission spectrum of several hot Jupiters. Studying the signature of these atomic lines not only can reveal the structure of the upper atmosphere, but also constrain the radiative cooling rates. To understand these features, we construct a sophisticated forward model by expanding the capability of the exoplanet hydrodynamic atmosphere code of Koskinen et al. (2013) to calculate processes of atomic metal species and compare the results with available observations. In the talk, I will explain our model and show the effect of metal species and Roche Lobe overflow.