A search for variable white dwarfs in large area time domain surveys: a pilot study in SDSS Stripe 82

TL;DR

This study develops a method to identify variable white dwarfs in large surveys and successfully finds several pulsating, magnetic, and binary white dwarfs in SDSS Stripe 82, including new ZZ Ceti stars.

Contribution

The paper introduces a reliable selection method for variable white dwarfs in large area time domain surveys and demonstrates its effectiveness with a pilot study in SDSS Stripe 82.

Findings

Identified 24 variable white dwarf candidates from 400 high-confidence samples.

Confirmed 5 new cool ZZ Ceti pulsators through follow-up observations.

Discovered additional variable types including an eclipsing binary and magnetic white dwarfs.

Abstract

We present a method to reliably select variable white dwarfs from large area time domain surveys and apply this method in a pilot study to search for pulsating white dwarfs in the Sloan Digital Sky Survey Stripe 82. From a sample 400 high-confidence white dwarf candidates, we identify 24 which show significant variability in their multi-epoch Stripe 82 data. Using colours, we further selected a sample of pulsating white dwarf (ZZ Ceti) candidates and obtained high cadence follow up for six targets. We confirm five of our candidates as cool ZZ Cetis, three of which are new discoveries. Among our 24 candidates we also identify: one eclipsing binary, two magnetic white dwarfs and one pulsating PG1159 star. Finally we discuss the possible causes for the variability detected in the remaining targets. Even with sparse multi-epoch data over the limited area of Stripe 82, we demonstrate that our selection method can successfully identify various types of variable white dwarfs and efficiently select high-confidence ZZ Ceti candidates.