Two new accreting, pulsating white dwarfs: SDSS J1457+51 and BW Sculptoris

TL;DR

This paper reports the discovery of two white dwarf pulsators with complex, rapidly changing signals, expanding the understanding of GW Lib class variables and their pulsation and orbital characteristics.

Contribution

The study identifies two new accreting, pulsating white dwarfs with detailed analysis of their complex periodic signals and orbital features, contributing to the knowledge of GW Lib class stars.

Findings

Detected rapid non-radial pulsations near 10 and 20 minutes.

Observed frequency changes over weeks indicating complex internal structures.

Identified orbital periods near 78 minutes and a superhump near 87 minutes.

Abstract

We report the discovery of rapid periodic signals in the light curves of two cataclysmic variables with prominent white-dwarf components in their spectra, SDSS J1457+51 and BW Sculptoris. These stars therefore appear to be new members of the GW Lib class of variable star, in which the fast periodic (and non-commensurate with the orbital period) signals are believed to arise from non-radial pulsations in the underlying white dwarf. The power spectra of both stars show complex signals with primary periods near 10 and 20 minutes. These signals change in frequency by a few percent on a timescale of weeks or less, and probably contain an internal fine structure unresolved by our observations. We also detect double-humped waves signifying the underlying orbital periods, near 78 minutes for both stars. In addition, BW Scl shows a transient but powerful signal with a period near 87 minutes, a quiescent superhump. The 11 % excess over the orbital period is difficult to understand, and may arise from an eccentric instability near the 2:1 resonance in the accretion disc.