Asteroseismology of WD J004917.14-252556.81, the Most Massive Pulsating White Dwarf

TL;DR

This paper presents detailed asteroseismology of the most massive known pulsating white dwarf, revealing its internal structure, composition, and rotation characteristics through extensive observational data and modeling.

Contribution

It provides the first detailed asteroseismic analysis of a ~1.3 solar mass white dwarf, including mode detection and interior modeling under an ONe core assumption.

Findings

13 pulsation modes detected, ranging from 170 to 258 seconds.

Best-fit models indicate a mass of approximately 1.29 solar masses.

Core is over 99% crystallized, with a thin hydrogen layer.

Abstract

We present extensive follow-up time-series photometry of WD J0049$-$2525, the most massive pulsating white dwarf currently known with $T_{\rm eff} = 13\, 020\,{\rm K}$ and $\log{\it g} = 9.34$ cm s$^{-2}$. The discovery observations detected only two significant pulsation modes. Here, we report the detection of 13 significant pulsation modes ranging from 170 to 258 s based on 11 nights of observations with the New Technology Telescope, Gemini, and Apache Point Observatory telescopes. We use these 13 modes to perform asteroseismology and find that the best-fitting models (under the assumption of an ONe core composition) have $M_{\star} \approx 1.29~M_\odot$, surface hydrogen layer mass of $\log(M_{\rm H}/M_{\star}) \lesssim -7.5$, and a crystallized core fraction of $>99\%$. An analysis of the period spacing also strongly suggests a very high mass. The asteroseismic distance derived is in good agreement with the distance provided by Gaia. We also find tentative evidence of a rotation period of 0.3 or 0.67 d. This analysis provides the first look at the interior of a $\sim 1.3~M_{\odot}$ white dwarf.