White Dwarf Variability with gPhoton: Pulsators

TL;DR

This study uses the gPhoton database to identify and analyze short-term variability in white dwarfs, discovering a new pulsator and providing multi-wavelength pulsation data for known ZZ Ceti stars.

Contribution

It introduces a novel application of gPhoton for white dwarf variability detection and characterizes a new pulsating white dwarf with multi-wavelength observations.

Findings

Discovery of a new pulsating white dwarf, WD 2246-069.

Detection of UV pulsations in four known ZZ Ceti stars.

Multi-wavelength analysis of WD 1401-147's pulsations.

Abstract

We present results from a search for short time-scale white dwarf variability using \texttt{gPhoton}, a time-tagged database of \textit{GALEX} photon events and associated software package. We conducted a survey of $320$ white dwarf stars in the McCook-Sion catalogue, inspecting each for photometric variability with particular emphasis on variability over time-scales less than $\sim 30$ minutes. From that survey, we present the discovery of a new pulsating white dwarf: WD 2246-069. A Ca II K line is found in archival ESO spectra and an IR excess is seen in WISE $W1$ and $W2$ bands. Its independent modes are identified in follow-up optical photometry and used to model its interior structure. Additionally, we detect UV pulsations in four previously known pulsating ZZ Ceti-type (DAVs). Included in this group is the simultaneous fitting of the pulsations of WD 1401-147 in optical, near-ultraviolet and far-ultraviolet bands using nearly concurrent Whole Earth Telescope and \textit{GALEX} data, providing observational insight into the wavelength dependence of white dwarf pulsation amplitudes.