Seven-Period Asteroseismic Fit of the Kepler DBV

TL;DR

This paper presents a detailed asteroseismic analysis of a helium-atmosphere white dwarf using seven observed pulsation modes, revealing a thin helium layer and potential for future cooling rate measurements.

Contribution

It provides a more constrained asteroseismic model with improved mode identification, supporting helium diffusion during DB cooling.

Findings

Identified at least seven pulsation modes with mode degree and order.

Detected a very thin helium layer in the white dwarf.

Modes appear stable, enabling future cooling rate measurements.

Abstract

We present a new, better-constrained asteroseismic analysis of the helium-atmosphere (DB) white dwarf discovered in the field of view of the original Kepler mission. Observations obtained over the course of two years yield at least seven independent modes, two more than were found in the discovery paper for the object. With several triplets and doublets, we are able to fix the $\ell$ and $\rm{m}$ identification of several modes before performing the fitting, greatly reducing the number of assumptions we must make about mode identification. We find a very thin helium layer for this relatively hot DB, which adds evidence to the hypothesis that helium diffuses outward during DB cooling. At least a few of the modes appear to be stable on evolutionary timescales and could allow us to obtain a measurement of the rate of cooling with monitoring of the star over the course of the next few years with ground-based follow-up.