The search for ZZ Ceti stars in the original Kepler mission

TL;DR

This paper reports the discovery of 42 white dwarfs in the Kepler field, including nine new ZZ Ceti pulsators, using photometric selection, spectroscopy, and space-based and ground-based photometry, advancing white dwarf asteroseismology.

Contribution

First identification of multiple ZZ Ceti stars in the Kepler field using combined photometric and spectroscopic methods.

Findings

Nine new ZZ Ceti pulsators confirmed.

Four of these were observed from space with Kepler.

The discoveries enhance the study of white dwarf pulsations.

Abstract

We report the discovery of 42 white dwarfs in the original Kepler mission field, including nine new confirmed pulsating hydrogen-atmosphere white dwarfs (ZZ Ceti stars). Guided by the Kepler-INT Survey (KIS), we selected white dwarf candidates on the basis of their U-g, g-r, and r-H_alpha photometric colours. We followed up these candidates with high-signal-to-noise optical spectroscopy from the 4.2-m William Herschel Telescope. Using ground-based, time-series photometry, we put our sample of new spectroscopically characterized white dwarfs in the context of the empirical ZZ Ceti instability strip. Prior to our search, only two pulsating white dwarfs had been observed by Kepler. Ultimately, four of our new ZZ Cetis were observed from space. These rich datasets are helping initiate a rapid advancement in the asteroseismic investigation of pulsating white dwarfs, which continues with the extended Kepler mission, K2.