Superhumps and post-outburst rebrightening episodes in the AM CVn star SDSS J012940.05+384210.4

TL;DR

This paper reports the first observed outburst of the AM CVn star SDSS J012940.05+384210.4, highlighting multiple rebrightening events, superhump detection, and archival evidence of outbursts in a similar system, advancing understanding of such phenomena.

Contribution

It provides the first detailed photometric observation of an outburst in SDSS J012940.05+384210.4, including rebrightening episodes and superhump analysis, and identifies outburst activity in another AM CVn system.

Findings

Six rebrightening events observed during the outburst.

Superhumps with a 37.9-minute period detected.

Archival data shows another AM CVn system also undergoes outbursts.

Abstract

We report unfiltered photometry of the first confirmed outburst of the AM CVn system SDSS J012940.05+384210.4 during 2009 December. At its brightest the star was magnitude 14.5, 5.4 magnitudes above mean quiescence. Although the first part of the outburst was not observed, six remarkable rebrightening events were observed during the course of the outburst. Forty-one days after the outburst was detected, the star was still 1.7 magnitudes above quiescence. Superhumps were observed during the outburst with a peak-to-peak amplitude of 0.06 mag and Psh = 37.9(2) min. We also used archival data to show that another AM CVn system, SDSS J124058.03-015919.2, has also undergone at least one outburst, with an amplitude of ~4.6 magnitudes.