2011CBET.2655....2M

P. A. Milne, University of Arizona; and S. B. Cenko, University of California, Berkeley, report that inspection of a CCD spectrum (range 400-830 nm), obtained on Feb. 13 UT with the 2.3-m Bok telescope (+ Boller and Chivens spectrograph), shows that 2011ac is a type-Ia supernova. After removal of the host-galaxy recession velocity of 14030 km/s (Falco et al. 1999, PASP 111, 438; via NED), they find the absorption minimum of the Si II 635.5-nm line to be blueshifted by about 12000 km/s. Cross-correlation with a library of supernova spectra using the "SuperNova IDentification" code (SNID; Blondin and Tonry 2007, Ap.J. 666, 1024) indicates that 2011ac is a normal type-Ia supernova shortly before maximum light.