A New Generation of Cool White Dwarf Atmosphere Models. II. A DZ Star with Collision-Induced Absorption

TL;DR

This paper applies advanced white dwarf atmosphere models to analyze a DZ star with collision-induced absorption, successfully fitting both metal lines and CIA, and explores implications for undetected metals in DC stars.

Contribution

It demonstrates the effectiveness of new atmosphere models in fitting complex spectral features of a DZ white dwarf with CIA, improving understanding of white dwarf atmospheres.

Findings

Successful fit of metal lines and CIA in the DZ star

Metal lines help resolve hydrogen abundance degeneracy

Undetected metals may influence photometric solutions of DC stars

Abstract

In the first paper of this series (Blouin et al. 2018), we presented our upgraded cool white dwarf atmosphere code. In this second paper, we use our new models to analyze SDSS J080440.63+223948.6 (J0804+2239), the first DZ star to show collision-induced absorption (CIA). This object provides a crucial test for our models, since previous versions of our code were unable to simultaneously fit the metal absorption lines and the CIA. We find an excellent fit to both the spectroscopic and photometric data, which further validates the improved constitutive physics of our models. We also show that the presence of metal lines allows to lift the degeneracy between high and low hydrogen abundances that usually affects the fits of white dwarfs with CIA. Finally, we investigate the potential impact of spectroscopically undetected metals on the photometric solutions of DC stars.