LS And: WZ Sge-type outburst first time since the 1971 discovery

TL;DR

This paper reports the first observed outburst of LS And since 1971, identifying it as a WZ Sge-type dwarf nova with detailed light curve analysis from ZTF data, confirming its classification and behavior.

Contribution

The study provides the first recent outburst data of LS And, confirming its classification as a WZ Sge-type dwarf nova and analyzing its light curve behavior over an extended period.

Findings

LS And underwent a second outburst in 2022 April.

The outburst behavior matches that of WZ Sge-type dwarf novae.

The object remains active on the fading tail more than a year after outburst.

Abstract

LS And was a transient discovered in 1971 in the M31 region and it has been argued whether it could be an intergalactic nova or a dwarf nova. Using the Zwicky Transient Facility (ZTF) data, I found that the object underwent the second known outburst in 2022 April. The behavior was that of a WZ Sge-type dwarf nova with a long fading tail and the light curves of the 1971 and 2022 outbursts matched very well. The light curves suggest that LS And is a typical WZ Sge-type dwarf nova near (but before reaching) the period minimum of cataclysmic variables. The true observed peak of the 1971 outburst was likely 12.2 mag. The outburst parameters were similar to those of other WZ Sge-type dwarf novae. The fading tail lasts more than a year and the object is still currently on this tail. There was a hint of 0.5-mag temporary brightening on the fading tail and the object appears still active after the outburst.