Multiple Outbursts of a Cataclysmic Variable in the Globular Cluster M22

Abstract

We present a 4 yr light curve of a cataclysmic variable in M22, based on an analysis of accumulated data from the Microlensing Observations in Astrophysics (MOA) microlensing survey. The position of the star coincides with that of a transient event observed by the Hubble Space Telescope (HST) in 1999, originally attributed to microlensing but later suspected to be a dwarf nova outburst. Two outburst episodes, one in 2002 and one in 2003, with ΔI ~ 3 are seen in the MOA data, thus confirming that the HST event was a dwarf nova outburst. The MOA and HST data show that this dwarf nova underwent at least three outburst episodes during 1999-2004. Further close monitoring of this event is encouraged, as future outburst episodes are expected.