Semi-Empirical Modeling of the M Dwarf Exoplanet Hosts GJ 832, GJ 581, and GJ 876: UV Radiation and Implications for Exoplanet Atmospheres

VIEYTES, MARIELA; JEFFREY LINSKY; TILIPMAN, DENNIS

Honolulu, Hawai

Congreso; 235th AAS Meeting; 2020

We constructed 1-D atmospheric semi-empirical models of the M dwarf exoplanet hosts GJ 832 (M2), GJ 581 (M3), and GJ 876 (M5), with the primary goal of synthesizing ultraviolet (UV) spectra of these stars. UV radiation drives photochemical processes in exoplanet atmospheres and can lead to atmospheric escape via hydrodynamic outflow. We compute our models in full non-LTE using the radiative transfer code SSRPM (Stellar-Solar Radiation Physical Modelling), and our model atmospheres extend from the photosphere to the corona. We use spectral data from the MUSCLES Treasury Survey and the 2.15 m telescope CASLEO in San Juan, Argentina. Our models fit spectra in the range from X-ray to visible, including key chromospheric lines such as Lyman alpha, Ca II h & k, Mg II h & k, C II (133.3 nm), and Si IV (140.0 nm). Thus, we can synthesize in a self-consistent manner the parts of electromagnetic spectra that are usually not available due to interstellar hydrogen absorption, specifically, far-UV (110 - 170 nm) continuum and all extreme-UV (10 - 91.2 nm) radiation. The output of our models can, therefore, be used as input for exoplanet atmosphere models.