Revisiting the theoretical DBV (V777 Her) instability strip: the MLT theory of convection

TL;DR

This paper reexamines the theoretical instability strip of pulsating DB white dwarfs using detailed nonadiabatic pulsation analysis and considers the effects of different convection models and atmospheric compositions.

Contribution

It provides a comprehensive analysis of the DBV instability strip considering evolutionary history, chemical diffusion, and convection prescriptions, offering refined theoretical predictions.

Findings

The location of the blue edge depends on convection treatment.

Small amounts of hydrogen influence the instability domain.

Evolutionary history affects pulsation properties.

Abstract

We reexamine the theoretical instability domain of pulsating DB white dwarfs (DBV or V777 Her variables). We performed an extensive $g$-mode nonadiabatic pulsation analysis of DB evolutionary models considering a wide range of stellar masses, for which the complete evolutionary stages of their progenitors from the ZAMS, through the thermally pulsing AGB and born-again phases, the domain of the PG1159 stars, the hot phase of DO white dwarfs, and then the DB white dwarf stage have been considered. We explicitly account for the evolution of the chemical abundance distribution due to time-dependent chemical diffusion processes. We examine the impact of the different prescriptions of the MLT theory of convection and the effects of small amounts of H in the almost He-pure atmospheres of DB stars on the precise location of the theoretical blue edge of the DBV instability strip.