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Discovery of a New Cataclysmic Variable by ROTSE-III

ATel #3651; J. Vinko (University of Szeged); W. Zheng (University of Michigan); R. Quimby (IPMU University of Tokyo); N. Whallon, A. Romadan, B. Sandler, and C. Akerlof (University of Michigan); F. Yuan (Australian National University); J. C. Wheeler and E. Chatzopoulos (University of Texas); G. H. Marion (Harvard-Smithsonian Center for Astrophysics) on behalf of the ROTSE collaboration
on 19 Sep 2011; 15:22 UT
Credential Certification: Jozsef Vinko (vinko@astro.as.utexas.edu)

Subjects: Optical, Cataclysmic Variable, Transient

We report the discovery of a new transient (mag ~14.9) in unfiltered images taken on Aug. 29.39 UT with the 0.45-m ROTSE-IIIb telescope at McDonald Observatory. The transient has brightened to mag ~14.0 on Aug. 30.42 then started to decay gradually in the following weeks with mag ~15.3 on Sep. 7.38 and mag ~16.1 on Sep. 14.37. The new object is located at R.A. = 03h44m50s.76, Decl. = +68o37'52".9 (equinox 2000.0; uncertainty about 1"). A finding chart for the object can be found at website URL: http://www.rotse.net/rsvp/j034450.8+683753/ROTSE3_J034450.8+683753.jpg A faint source is present at the position of the transient on the POSS-II images with USNO B1.0 magnitudes R=19.77 and I=18.85. A spectrum obtained with the 9.2-m Hobby-Eberly Telescope (+Marcario Low-Resolution Spectrograph, R ~ 600) by J. Caldwell on 2011. Sept. 1.46 UT shows narrow absorption features, including Na-D, H-beta and H-gamma at zero redshift, superimposed on a smooth blue continuum. H-alpha is filled up by an emission component, but does not extend above the continuum. A second spectrum obtained on Sept. 17.42 UT by S. Rostopchin has the same overall appearance, but with flatter, redder continuum slope. The spectroscopic observations together with the identification of a stellar-like source at this position, suggest that the transient is galactic, probably an outburst of a cataclysmic variable. Monitoring with the ROTSE-III telescopes is continuing.