An analysis of metallic high ion absorption line profiles at DA white dwarfs with circumstellar material

TL;DR

This study analyzes unresolved high ion absorption lines in six hot white dwarfs to understand circumstellar effects on photospheric abundance estimates, proposing a new modeling approach for these spectral features.

Contribution

It provides the first detailed analysis of unresolved metal high ion lines in white dwarfs, highlighting the impact of circumstellar material on abundance measurements and introducing a novel modeling technique.

Findings

Circumstellar features reduce derived photospheric C IV abundances.

Weak circumstellar Si IV causes modest abundance revisions.

Proposes a new line profile modeling method for better insights.

Abstract

Some hot DA stars exhibit circumstellar absorption in the metal resonance lines in their spectra. In many cases, these circumstellar features are unresolved from those originating in the photosphere. To better understand the effect this circumstellar blending has on photospheric abundance estimates, we present here an analysis of the unresolved metal high ion absorption features of six hot white dwarfs. In all cases, given the strong circumstellar C IV detections, the photospheric C IV abundances are reduced; conversely the weak circumstellar Si IV leads to modest photospheric abundance revisions. A possible new technique for modelling these line profiles is discussed, that can better reproduce the observations and provide a greater insight into the conditions of the circumstellar medium.