The Pulsating Helium-Atmosphere White Dwarfs I: New DBVs from the Sloan Digital Sky Survey

TL;DR

This study identifies 19 new helium-atmosphere pulsating white dwarfs (DBVs) from SDSS data, refining the empirical boundaries of the DB instability strip and analyzing their pulsation properties.

Contribution

The paper reports the discovery of new DBVs, updates the empirical instability strip boundaries, and compares pulsation properties across white dwarf types.

Findings

19 new DBVs discovered from SDSS data.

Red edge of the instability strip is better constrained.

Pulsation properties show trends with temperature similar to hydrogen-atmosphere white dwarfs.

Abstract

We present a dedicated search for new pulsating helium-atmosphere (DBV) white dwarfs from the Sloan Digital Sky Survey using the McDonald 2.1m Otto Struve Telescope. In total we observed 55 DB and DBA white dwarfs with spectroscopic temperatures between 19,000 and 35,000K. We find 19 new DBVs and place upper limits on variability for the remaining 36 objects. In combination with previously known DBVs, we use these objects to provide an update to the empirical extent of the DB instability strip. With our sample of new DBVs, the red edge is better constrained, as we nearly double the number of DBVs known between 20,000 and 24,000K. We do not find any new DBVs hotter than PG 0112+104, the current hottest DBV at $T_{\mathrm{eff}}\,{\approx}$ 31,000K, but do find pulsations in four DBVs with temperatures between 27,000 and 30,000K, improving empirical constraints on the poorly defined blue edge. We investigate the ensemble pulsation properties of all currently known DBVs, finding that the weighted mean period and total pulsation power exhibit trends with effective temperature that are qualitatively similar to the pulsating hydrogen-atmosphere white dwarfs.