2009CBET.1775....1Y

F. Yuan, University of Michigan; J. Vinko, University of Texas; R. Quimby, California Institute of Technology; D. Chamarro, M. D. Sisson, and C. Akerlof, University of Michigan; and J. C. Wheeler and E. Chatzopoulos, University of Texas, on behalf of the ROTSE collaboration, report the discovery of an apparent supernova (mag 17.5 ± 0.2) in unfiltered CCD images taken on Apr. 12.78 UT with the 0.45-m ROTSE-IIId telescope at the TUBITAK National Observatory at Bakirlitepe, Turkey. The transient was discovered by subtracting a reference image constructed from images taken in 2008 (limiting mag 19.2), and it was also detected with the ROTSE-IIIb telescope at the McDonald Observatory at a similar magnitude on Apr. 11, 14, 15, and 16 (but not detected on Apr. 7.16 to a limiting magnitude of about 18.3); the photometric uncertainties are relatively large due to image subtraction. The new object is located at R.A. = 11:37:39.33, Decl. = +46:57:11.3 (equinox 2000.0; uncertainty about 1"), which is 3".0 east and 2".5 south of the center of its apparent host galaxy, 2MASX J11373899+4657141. Given the redshift of the presumed host (z = 0.039, measured via the Sloan Digital Sky Survey) and the observed light curve, 2009dn is likely to be a supernova discovered around peak brightness. The location of 2009dn is shown in the chart posted at URL http://rotse.net/rsvp/j113739.3+465711/j113739.3+465711.jpg. Note that 2009dn is blended with the apparent host galaxy, due to the large pixel scale (3".3) of ROTSE-III.