GALEX and Optical Observations of GW Librae During the Long Decline from Superoutburst

TL;DR

This study tracks the long-term post-outburst evolution of GW Librae using UV and optical data, revealing various periodic modulations and the slow return of pulsations over three years.

Contribution

It provides a detailed multi-year observational analysis of GW Lib's post-outburst behavior, highlighting new long-term variability patterns.

Findings

Detection of superhump modulation post-outburst

Identification of a 19-minute quasi-periodic modulation

Observation of a 4-hour UV variation increasing over years

Abstract

The prototype of accreting, pulsating white dwarfs (GW Lib) underwent a large amplitude dwarf nova outburst in 2007. We used ultraviolet data from GALEX and ground-based optical photometry and spectroscopy to follow GW Lib for three years following this outburst. Several variations are apparent during this interval. The optical shows a superhump modulation in the months following outburst while a 19 min quasi-periodic modulation lasting for several months is apparent in the year after outburst. A long timescale (about 4 hr) modulation first appears in the UV a year after outburst and increases in amplitude in the following years. This variation also appears in the optical 2 years after outburst but is not in phase with the UV. The pre-outburst pulsations are not yet visible after 3 years, likely indicating the white dwarf has not returned to its quiescent state.