Understanding the spectrum of the very hot DA white dwarf PG0948+534

TL;DR

This paper analyzes the UV spectrum of the extremely hot and mysterious DA white dwarf PG0948+534, identifying absorption features, circumstellar material, and determining its atmospheric composition and physical parameters.

Contribution

It provides the first detailed abundance measurements and revised temperature and gravity estimates for PG0948+534 using advanced non-LTE models.

Findings

Detected over 300 absorption features and four velocity regimes.

Identified circumstellar absorption in C IV and Si IV lines.

Revised stellar parameters and elemental abundances.

Abstract

PG0948+534 is currently one of the hottest DA white dwarf stars, and is also one of the most mysterious. Attempts to model the sharp, deep absorption features of this star have been unsuccessful. In these proceedings we describe our analysis of PG0948+534. We perform a line survey of the UV spectrum of PG0948+534, making detections of 300+ absorption features, and identifying four distinct velocity regimes. We find evidence of circumstellar absorption in the profiles of C {\sc iv} and Si {\sc iv}. Using non-local thermodynamic equilibrium model atmospheres, we are able to correctly model the absorption features of the star, providing abundance measurements for C, N, O, and Si for PG0948+534 for the first time. We also revise the effective temperature and gravity for this star using models including these new abundances.