The white dwarf in dwarf nova SDSS J080434.20+510349.2: Entering the instability strip?

TL;DR

This study observes the white dwarf in SDSS J080434.20+510349.2, a dwarf nova, noting the emergence of pulsations post-outburst likely as the white dwarf cooled into the instability strip, with detailed analysis of its pulsation evolution.

Contribution

First detection of non-radial pulsations in the white dwarf of SDSS J080434.20+510349.2 after outburst, linking pulsation onset to cooling into the instability strip.

Findings

Pulsations appeared approximately 8 months after outburst.

Pulsation period of 12.6 minutes with 0.05 magnitude amplitude.

Pulsations likely triggered as the white dwarf cooled into the instability strip.

Abstract

SDSS J080434.20+510349.2 is the WZ type binary that displayed rare outburst in 2006 (Pavlenko et al., 2007). During the long-lasting tail of the late stage of the outburst binary shown the two-humped or four-humped profile of the orbital light modulation. The amplitude of orbital light curve decreased while the mean brightness decreased, more over that occurred $\sim$ 10 times faster during the fast outburst decline in respect to the late quiet state of slow outburst fading. There were no white dwarf pulsations detected neither 1 - 1.5 months prior to the outburst nor in 1.5 - 2 months after the 2006 outburst in this system. However the strong non-radial pulsations with period 12.6 minutes and mean amplitude of 0.05^m were first detected in V band with 2.6-m Shajn mirror telescope of the Crimean astrophysical observatory in ~ 8 months after the outburst. The evolution of pulsations over two years in 2006 - 2008 is considered. It is supposed that pulsations first appeared when the cooling white dwarf (after the outburst) entered the instability strip although the possibility of temporary lack of pulsations at some occasions also could not be excluded.