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Infrared detection of a dwarf nova eruption in the globular cluster M22 by the VVV survey

ATel #7238; J. Alonso-Garcia (Pontificia Universidad Catolica de Chile, Millennium Institute of Astrophysics), D. Minniti (Universidad Andres Bello, Vatican Observatory, Millennium Institute of Astrophysics), R. Angeloni (Gemini Observatory), R. K. Saito (Universidade Federal de Sergipe), M. Catelan (Pontificia Universidad Catolica de Chile, Millennium Institute of Astrophysics), I. Dekany (Millennium Institute of Astrophysics, Pontificia Universidad Catolica de Chile), R. Contreras Ramos (Pontificia Universidad Catolica de Chile, Millennium Institute of Astrophysics)
on 17 Mar 2015; 13:28 UT
Credential Certification: Javier Alonso-Garcia (jalonso@astro.puc.cl)

Subjects: Infra-Red, Cataclysmic Variable, Globular Cluster

We report a new dwarf nova outburst in the cataclysmic variable CV1 in the Galactic globular cluster M22. The reported outburst happened in the first weeks of August 2014. In the VVV Survey data (Minniti et al. 2010, New Astronomy, 15, 433), we observe an increment in brightness of more than 1 magnitude in Ks from the average magnitude of this star (Ks~16; see Figure 1). The VVV Survey coordinates for this object are (RA,Dec)=18:36:24.69,-23:54:35.5. The observation of this new outburst adds to the increasing evidence that this star is a cataclysmic variable ( Anderson et al. 2003, ApJ, 597, L137; Bond et al. 2005, 620, L103; Pietrukowicz et al. 2005, Acta Astronomica, 55, 261; Hourihane 2011, MNRAS, 414, 184), instead of a microlensing event as reported in the discovery paper (Sahu et al. 2001, Nature, 411, 10022). VVV data for the outburst fit in the 20-25 day window that previous outbursts were reported to last, although our coverage is reduced to only 3 days while the outburst lasted. Further confirmation from other surveys observing this region at the time of the outburst, like OGLE, would be useful. The reported outburst is the first dwarf nova eruption in a cataclysmic variable that has been observed at near-infrared wavelengths in a Galactic globular cluster.

Acknowledgments: We gratefully acknowledge use of data from the ESO Public Survey programme ID 179.B-2002 taken with the VISTA telescope. J.A.-G. and R.C.R. acknowledges support from Proyecto Fondecyt Postdoctoral 3130552 and 3130320 respectively.