Asteroseismology of the DAV star R808

TL;DR

This study uses extensive observational data and advanced modeling to identify pulsation modes in the DAV star R808, achieving the most precise asteroseismological fit to date and providing insights into its internal structure.

Contribution

It presents a detailed asteroseismological analysis of R808 using models with element diffusion and core compositions from MESA, achieving the smallest RMS period difference among similar studies.

Findings

Best fitting model has log($M_{He}/M_*$) = -2.4 and $T_{eff}$ = 11100 K.

Achieved the smallest RMS period difference (2.86 s) among existing studies.

Detected potential $l$=2 trapped mode in the observed pulsations.

Abstract

The DAV star R808 was observed by 13 different telescopes for more than 170 hours in April 2008 on the WET run XCOV26. 25 independent pulsation frequencies were identified by this data set. We assumed 19 $m$ = 0 modes and performed an asteroseismological study on those 19 modes. We evolve grids of DAV star models by \texttt{WDEC} adopting the element diffusion scheme with pure and screened Coulomb potential effect. The core compositions are from white dwarf models evolved by \texttt{MESA}, which are thermal nuclear burning results. Our best fitting model is from the screened Coulomb potential scenario, which has parameters of log($M_{\rm He}/M_{\rm *}$) = -2.4, log($M_{\rm H}/M_{\rm *}$) = -5.2, $T_{\rm eff}$ = 11100\,K, $M_{\rm *}$ = 0.710\,$M_{\odot}$, log$g$ = 8.194, and $\sigma_{RMS}$ = 2.86\,s. The value of $\sigma_{RMS}$ is the smallest among the four existing asteroseismological work. The average period spacing is 46.299\,s for $l$ = 1 modes and 25.647\,s for $l$ = 2 modes. The other 6 observed modes can be fitted by $m$ $\neq$ 0 components of some modes for our best fitting model. Fitting the 25 observed modes, we obtain a $\sigma_{RMS}$ value of 2.59\,s. Considering the period spacings, we also assume, that at least in one case, we detect an $l$ = 2 trapped mode.