2010CBET.2557....1Z

W. Zheng, University of Michigan; J. Vinko, University of Szeged; R. Quimby, California Institute of Technology; A. Romadan, N. Whallon, S. B. Pandey, F. Yuan, and C. Akerlof, University of Michigan; P. Pasque and M. Verkinderen, Cousino High School; and J. C. Wheeler and E. Chatzopoulos, University of Texas, on behalf of the ROTSE collaboration, report the discovery of a new supernova (mag about 18.1) in unfiltered images taken on Nov. 14.34 UT with the 0.45-m ROTSE-IIIb telescope at McDonald Observatory. The new object – which was observed again on Nov. 23.11 at mag about 18.0 and on Nov. 24.06 at mag about 18.2 – is located at R.A. = 0:57:24.62, Decl. = -0:57:51.4 (equinox 2000.0; uncertainty about 1"), which is 0".2 east and 1".9 south of the center of the presumed host galaxy (SDSS J005724.60-005749.5). A finding chart for the object can be found at website URL http://www.rotse.net/rsvp/j005724.6-005751/j005724.6-005751.jpg. A spectrum, obtained on Nov. 25.10 UT with the 9.2-m Hobby-Eberly Telescope (+ Marcario Low-Resolution Spectrograph) by S. Odewahn, shows 2010ke to be a type-Ia supernova at more than a week after maximum light. The spectrum contains a strong Si II feature and several other broad lines of S II and Fe II, characteristics of type-Ia supernovae. The best-matching template spectrum in SNID (Blondin and Tonry 2007, ApJ. 666, 1024) is to the spectrum of SN 1995E at 10 days after maximum. The redshift, estimated from broad supernova features, is z = 0.042, consistent with the photo-z estimate of the presumed host galaxy in the SDSS database. The expansion velocity at the photosphere, derived from the absorption minimum of the Si II 635.5-nm feature, is about 10000 km/s.