Application of screened Coulomb potential in fitting DBV star PG 0112+104

TL;DR

This study compares pure and screened Coulomb potentials in white dwarf models to improve asteroseismic fits for the pulsating DB star PG 0112+104, finding that the screened potential reduces fitting errors and enhances model accuracy.

Contribution

It introduces the use of screened Coulomb potential in white dwarf models to better fit observed pulsation modes of PG 0112+104, improving the asteroseismic fit accuracy.

Findings

Screened Coulomb potential reduces RMS fitting error by 4%.

Model fit accuracy improves by 27% with screened potential.

Optimal models align with previous spectroscopic and asteroseismological results.

Abstract

With 78.7 days of observations for PG 0112+104, a pulsating DB star, from Campaign 8 of $Kepler$ 2 mission, Hermes et al. made a detailed mode identification. A reliable mode identification, with 5 $l$ = 1 modes, 3 $l$ = 2 modes, and 3 $l$ = 1 or 2 modes, was identified. Grids of DBV star models are evolved by \texttt{WDEC} with element diffusion effect of pure Coulomb potential and screened Coulomb potential. Fitting the identified modes of PG 0112+104 by the calculated ones, we studied the difference of element diffusion effect between adopting pure Coulomb potential and screened Coulomb potential. Our aim is to reduce the fitting error by studying new input physics. The starting models including their chemical composition profile are from white dwarf models evolved by \texttt{MESA}. They were calculated following the stellar evolution from the main sequence to the start of the white dwarf cooling sequences. The optimal parameters are basically consistent with that of previous spectroscopic and asteroseismological studies. The pure and screened Coulomb potential lead to different composition profiles of the C/O-He interface area. High $k$ modes are very sensitive to the area. However, most of the observed modes for PG 0112+104 are low $k$ modes. The $\sigma_{RMS}$ taking the screened Coulomb potential is reduced by 4\% compared with taking the pure Coulomb potential when fitting the identified low $k$ modes of PG 0112+104. Fitting the $Kepler$ 2 data with our models improved the $\sigma_{RMS}$ of the fit by 27\%.