Line Profiles of the Calcium I Resonance Line in Cool Metal-polluted White Dwarfs

Understand

Metal-polluted white dwarfs (DZ stars) are characterized by a helium-rich atmosphere contaminated by heavy elements traces originating from accreted rocky planetesimals.

• As a detailed spectroscopic analysis of those objects can reveal the composition of the accreted debris, there is a great interest in developing accurate DZ atmosphere models.
• However, the coolest DZ white dwarfs are challenging to model due to the fluidlike density of their atmospheres.
• Under such extreme conditions, spectral absorption lines are heavily broadened by interactions with neutral helium and it is no longer justified to use the conventional Lorentzian profiles.