Multiple Outbursts of a Cataclysmic Variable in the Globular Cluster M22
Sumi, T.; MOA Collaboration; Bond, I. A.; Abe, F.; Matsubara, Y.; Muraki, Y.; Sullivan, D. J.; Tristram, P. J.; Sako, T.; Yock, P. C. M.; Hearnshaw, J. B.; Rattenbury, N. J.; Kamiya, K.; Kilmartin, P. M.; Masuda, K.; Yanagisawa, T.; Furuta, Y.; Kurata, Y.; Noda, S.; Okajima, K.; Sekiguchi, T.; Eguchi, S.
New Zealand, Japan, United Kingdom, United States
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.