2009CBET.1666....1Y

F. Yuan, University of Michigan; J. Vinko, University of Texas; R. Quimby, California Institute of Technology; D. Chamarro and M. D. Sisson, University of Michigan; A. Uecker, Indiana University of Pennsylvania; 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 a supernova (mag about 16.8) in unfiltered CCD images taken on Jan. 13.44 UT with the 0.45-m ROTSE-IIIb telescope at McDonald Observatory. The new object is located at R.A. = 12h58m48s.10, Decl. = +27o40'25".6 (equinox 2000.0), which is 8".4 east and 3".9 south of the center of its apparent host galaxy, NGC 4854. A finding chart FOR 2009L has been posted at http://www.rotse.net/rsvp/j125848.1+274026/j125848.1+274026.jpg. A spectrum (range 340-1080 nm) of 2009L, obtained on Jan. 15.34 with the 9.2-m Hobby-Eberly Telescope (+ Marcario Low-Resolution Spectrograph) by J. Caldwell and A. Westfall, shows it to be a type-Ia supernova. SNID (Blondin and Tonry 2007, Ap.J. 666, 1024) indicates that the spectra best match the spectra of SNe 1999by and 1991bg at 3 days after maximum and at a redshift consistent with that of NGC 4854. The expansion velocity, derived from the minimum of the Si II (rest 635.5 nm) line, is about 11000 km/s. The (580 nm)/(615 nm) line-depth ratio (Nugent et al. 1995, Ap.J. 455, L147) for Si II is about 0.5, indicating a subluminous type-Ia event. Strong, broad absorption features at 760 and 850 nm (attributed to O I and Ca II) are also present, which strongly supports this classification (Garnavich et al. 2004, Ap.J. 613, 1120).