Evidence of Resonant Mode Coupling in the Pulsating DB White Dwarf Star KIC 08626021

TL;DR

This study analyzes nearly two years of Kepler data on the pulsating white dwarf KIC 08626021, revealing clear evidence of nonlinear resonant mode coupling that aligns with theoretical models and could enable new asteroseismic diagnostics.

Contribution

It provides the first observational evidence of resonant mode coupling in a white dwarf star using space-based data.

Findings

Detected nonlinear resonant mode coupling in KIC 08626021

Observed amplitude and frequency modulations consistent with theory

Potential to measure linear growth rates of pulsation modes

Abstract

The Kepler spacecraft provides new opportunities to search for long term frequency and amplitude modulations of oscillation modes in pulsating stars. We ana- lyzed nearly two years of uninterrupted data obtained with this instrument on the DBV star KIC 08626021 and found clear signatures of nonlinear resonant mode coupling af- fecting several triplets. The behavior and timescales of these amplitude and frequency modulations show strong similarities with theoretical expectations. This may pave the way to new asteroseismic diagnostics, providing in particular ways to measure for the first time linear growth rates of pulsation modes in white dwarf stars.