Asteroseismic constraints on diffusion in WD envelopes

TL;DR

This paper uses asteroseismology to analyze the internal structure of the hottest known pulsating helium atmosphere white dwarf, EC20058-5234, providing insights into diffusion processes and stellar evolution at high temperatures.

Contribution

It presents the first detailed asteroseismic analysis of EC20058-5234, confirming helium envelope thickness consistent with diffusion models and improving mode identification.

Findings

Helium envelope thickness matches diffusion predictions.

Precise mode identification achieved for EC20058-5234.

Results link white dwarf cooling and neutrino emission processes.

Abstract

The asteroseismic analysis of white dwarfs allows us to peer below their photospheres and determine their internal structure. At ~ 28,000 K EC20058-5234 is the hottest known pulsating helium atmosphere white dwarf. As such, it constitutes an important link in the evolution of white dwarfs down the cooling track. It is also astrophysically interesting because it is at a temperature where white dwarfs are expected to cool mainly through the emission of plasmon neutrinos. In the present work, we perform an asteroseismic analysis of EC20058-5234 and place the results in the context of stellar evolution and time dependent diffusion calculations. We use a parallel genetic algorithm complemented with targeted grid searches to find the models that fit the observed periods best. Comparing our results with similar modeling of EC20058-5234's cooler cousin CBS114, we find a helium envelope thickness consistent with time dependent diffusion calculations and obtain a precise mode identification for EC20058-5234.