V386 Ser: A Classic Case of an Accreting, Pulsating White Dwarf

A pulsating white dwarf in a cataclysmic variable that undergoes a dwarf nova outburst presents a unique astronomical laboratory to study the instability strip under conditions of increased metal abundance, spin and mass compared to single pulsating white dwarfs. The main advantage is the heating from the outburst and subsequent cooling occurs on timescales of months-years compared to the millenia of evolutionary cooling. Using COS ultraviolet spectra from HST combined with ground optical data, we have followed the prototype GW Lib for the past 13 years after its outburst in 2007 and most recently, followed V386 Ser since its January 2019 outburst. These 2 systems both have similar orbital periods and had very large amplitude outbursts, yet showed quite different cooling scenarios. While GW Lib revealed various long and short pulsation periods during its long outburst cooling, V386 Ser so far shows the classic theoretical expectation for the driving modes at shorter periods soon after outburst heating, followed by lengthening periods as the white dwarf cools. We will show the recent data on V386 Ser in comparison to GW Lib. This research was partially supported by NASA grants HST-GO-14912, HST-GO-16046, and NSF Grant AST-1514737.