[vsnet-outburst 10378] Re: ROTSE3 J203225+602837 outburst

[Howard E. Bond]

Taichi Kato wrote:
> 
>    ROTSE3 J203225+602837 outburst (the object was already reported in
> ATEL #1642).  The light curve and the recurrence time (~1 year?) might
> suggest a superoutburst.
> 
> ===
> 
> ATEL #2126                                                           ATEL #2126
> 
> Title:          ROTSE-III discovery of a new Cataclysmic Variable
> Author: J. Vinko, University of Texas; F. Yuan, University of Michigan;
>                  R.  Quimby, California Institute of Technology; Z. Balog, University
>                 of  Arizona; D. Chamarro, M. D. Sisson, C. Akerlof, S. B. Pandey,
>                 University of Michigan; J. C. Wheeler and E. Chatzopoulos,  University
>                 of Texas, on behalf of the ROTSE collaboration
> Queries:        yuanfang at umich.edu
> Posted: 11 Jul 2009;  5:13  UT
> Subjects:       Optical, Cataclysmic Variables, Transients, Variables
> 
> We report the discovery of a transient ROTSE3J203224.8+602837    on unfiltered
> CCD images taken on Jul. 06.82 UT with the 0.45-m ROTSE-IIId    telescope
> at the TUBITAK National Observatory at Bakirlitepe, Turkey, and    confirmed
> by the 0.45-m ROTSE-IIIb telescope at McDonald Observatory,    Texas. The
> transient was discovered by subtracting a reference image    constructed
> from frames taken in 2008 (limiting mag 18.5). The brightness    of the
> source was 16.05 +/- 0.1 mag (unfiltered, tied to USNO B1.0 R-mag)
> at the time of discovery. The transient was subsequently detected between
> Jul. 7 and 10, declining to 16.4 +/- 0.2 mag on Jul.    10.26 UT. 


I would like to point out that ROTSE3 J203225+602837 lies within ~13' of the
center of the rich open cluster NGC 6939.  As pointed out by Kafka, Gibbs,
Henden, & Honeycutt (2004, AJ, 127, 1622), the number of CV's known in open
clusters is extremely small, only 3 according to Kafka et al.

Kafka et al. searched unsuccessfully for CV's in NGC 6939 during 5 months of
monitoring. They point out, however, that a DN at maximum belonging to NGC 6939
would have an apparent magnitude of V ~ 16, which is very close to the value
reported by the ROTSE team.

Thus an effort to establish the cluster membership of the new CV, e.g. through
radial velocities and proper motions, would be valuable.

Howard E. Bond
Space Telescope Science Institute