Pressure Distortion of the H$_2$-He Collision-Induced Absorption at the Photosphere of Cool White Dwarf Stars

Understand

Collision-induced absorption (CIA) from molecular hydrogen is a dominant opacity source in the atmosphere of cool white dwarfs.

• It results in a significant flux depletion in the near-IR and IR parts of their spectra.
• Because of the extreme conditions of helium-rich atmospheres (where the density can be as high as a few g/cm$^3$), this opacity source is expected to undergo strong pressure distortion and the currently used opacities have not been validated at such extreme conditions.
• To check the distortion of the CIA opacity we applied state-of-the-art ab initio methods of computational quantum chemistry to simulate the CIA opacity at high densities.