2008CBET.1500....1Y

F. Yuan, University of Michigan; R. Quimby, California Institute of Technology; A. Uecker, Indiana University of Pennsylvania; D. Chamarro, M. D. Sisson, and C. Akerlof, University of Michigan; and J. C. Wheeler, University of Texas, on behalf of the ROTSE collaboration, report the discovery of a supernova (mag about 17.5) in unfiltered CCD images taken on Sept. 5.16, 6, and 7 UT with the 0.45-m ROTSE-IIIb telescope at McDonald Observatory. The new object is located at R.A. = 23h49m03s.51, Decl. = +26o47'39".3 (equinox 2000.0), which is 25".2 east and 22".0 north of the center of its apparent host galaxy, UGC 12792. A finding chart has been posted at the following website URL: http://www.rotse.net/rsvp/j234903.5+264739/j234903.5+264739.jpg. A spectrum (range 420-890 nm) of 2008fm, obtained on Sept. 7.20 with the 9.2-m Hobby-Eberly Telescope (+ Marcario Low-Resolution Spectrograph) by J. Caldwell and E. Terrazas, shows it to be a type-IIn supernova; the redshift derived from the hydrogen Balmer emission lines is consistent with that of the presumed host, UGC 12792 (z = 0.0385; Zabludoff et al. 1990, Ap.J. Suppl. 74, 1).