Long-term Photometric Behavior of Outbursting AM CVn Systems

TL;DR

This study analyzes long-term photometric data of outbursting AM CVn systems over nearly a decade, revealing how their outburst behavior correlates with orbital periods and expanding understanding of their variability states.

Contribution

It provides a comprehensive analysis of AM CVn systems' long-term light curves, establishing relations between outburst properties and orbital periods, and explaining their evolutionary behavior.

Findings

Outburst properties correlate with orbital periods.

Some systems show only a single outburst.

Outburst evolution is linked to decreasing mass transfer rates.

Abstract

The AM CVn systems are a class of He-rich, post-period minimum, semi-detached, ultra-compact binaries. Their long-term light curves have been poorly understood due to the few systems known and the long (hundreds of days) recurrence times between outbursts. We present combined photometric light curves from the LINEAR, CRTS, and PTF synoptic surveys to study the photometric variability of these systems over an almost 10 yr period. These light curves provide a much clearer picture of the outburst phenomena that these systems undergo. We characterize the photometric behavior of most known outbursting AM CVn systems and establish a relation between their outburst properties and the systems' orbital periods. We also explore why some systems have only shown a single outburst so far and expand the previously accepted phenomenological states of AM CVn systems. We conclude that the outbursts of these systems show evolution with respect to the orbital period, which can likely be attributed to the decreasing mass transfer rate with increasing period. Finally, we consider the number of AM CVn systems that should be present in modeled synoptic surveys.