New study of the line profiles of sodium perturbed by H2

The opacity of alkali atoms, most importantly of Na and K, plays a crucial role in the atmospheres of brown dwarfs and exoplanets. We present a comprehensive study of Na-H₂ collisional profiles at temperatures from 500 to 3000 K, the temperatures prevailing in the atmosphere of brown dwarfs and Jupiter-mass planets. The relevant H₂ perturber densities reach several 10¹⁹ cm^-3 in hot (T_eff ≳ 1500 K) Jupiter-mass planets and can exceed 10²⁰ cm^-3 for more massive or cooler objects. Accurate pressure-broadened profiles that are valid at high densities of H₂ should be incorporated into spectral models. Unified profiles of sodium perturbed by molecular hydrogen were calculated in the semi-classical approach using up-to-date molecular data. New Na-H₂ collisional profiles and their effects on the synthetic spectra of brown dwarfs and hot Jupiters computed with petitCODE are presented.

Opacity tables are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/628/A120