Discovery of ZZ cetis in detached white dwarf plus main-sequence binaries

Abstract

We present the first results of a dedicated search for pulsating white dwarfs (WDs) in detached WD plus main-sequence (MS) binaries. Candidate systems were selected from a catalogue of WD+MS binaries, based on the surface gravities and effective temperatures of the WDs. We observed a total of 26 systems using ULTRACAM mounted on ESO's 3.5 m New Technology Telescope at La Silla. Our photometric observations reveal pulsations in seven WDs of our sample, including the first pulsating WD with an MS companion in a post-common envelope (CE) binary, SDSS J1136+0409. Asteroseismology of these new pulsating systems will provide crucial insight into how binary interactions, particularly the CE phase, affect the internal structure and evolution of WDs. In addition, our observations have revealed the partially eclipsing nature of one of our targets, SDSS J1223-0056