Asteroseismology of the ultramassive ZZ Ceti star WD 0246+326

TL;DR

This study uses asteroseismology to analyze the internal structure of the ultramassive ZZ Ceti star WD 0246+326, revealing its rotation period, mode spacings, and stellar parameters through time series photometry.

Contribution

First detailed asteroseismic analysis of WD 0246+326, providing its rotation period, mode identification, and stellar parameters, advancing understanding of massive white dwarf structures.

Findings

Rotation period of 3.78 days derived

Average period spacing of 29.3 seconds for l=1 modes

Stellar mass estimated at 0.98 solar masses

Abstract

The internal structures of pulsating white dwarfs can be explored only with asteroseismology. Time series photometric observations were made for the pulsating DA white dwarf (ZZ Ceti star) WD~0246+326 during 9 nights in 2014 with a bi-site observation campaign. Eleven frequencies were detected including 1 triplet, 2 doublets, and 4 single modes, which are identified as either $l=1$ or $l=2$ modes with the complementarity of frequencies present in the literature. From the multiplets, the rotation period of \astrobj{WD~0246+326} is derived as $3.78\pm 0.11$ days. The average period spacing of the l=1 modes $\Delta P=29.3\pm 0.2s$, implies that \astrobj{WD~0246+326} may be a massive ZZ Ceti star concerning the $\Delta P-M_*$ relationship for the DAVs. Preliminary analysis derives the stellar parameters of $M_*=0.98\pm0.01$~${\rm M_\odot}$ and $T_{\rm eff}=11700\pm100$~K by fitting the theoretical frequencies of the eigen modes to the observed ones.