Searching for ZZ Ceti White Dwarfs in the Gaia Survey

TL;DR

This study used Gaia data combined with photometry to identify and discover 38 new ZZ Ceti white dwarf pulsators, including rare ultra-massive ones, and analyzed their variability and properties.

Contribution

It presents the first large-scale identification of ZZ Ceti candidates using Gaia data, leading to the discovery of new pulsators and insights into the instability strip.

Findings

Discovered 38 new ZZ Ceti stars, including ultra-massive pulsators.

Identified 5 possibly variable stars within the instability strip.

Analyzed the period and amplitude trends in the mass-temperature plane.

Abstract

The {\it Gaia} satellite recently released parallax measurements for $\sim$260,000 high-confidence white dwarf candidates, allowing for precise measurements of their physical parameters. By combining these parallaxes with Pan-STARRS and $u$-band photometry, we measured the effective temperature and stellar mass for all white dwarfs in the Northern Hemisphere within 100 parsecs of the Sun, and identified a sample of ZZ Ceti white dwarf candidates within the so-called instability strip. We acquired high-speed photometric observations for 90 candidates using the PESTO camera attached to the 1.6-m telescope at the Mont-M\'egantic Observatory. We report the discovery of 38 new ZZ Ceti stars, including two very rare ultra-massive pulsators. We also identified 5 possibly variable stars within the strip, in addition to 47 objects that do not appear to show any photometric variability. However, several of those could be variable with an amplitude below our detection threshold, or could be located outside the instability strip due to errors in their photometric parameters. In the light of our results, we explore the trends of the dominant period and amplitude in the $M - T_{\rm eff}$ plane, and briefly discuss the question of the purity of the ZZ Ceti instability strip (i.e. a region devoid of non-variable stars).