Supernova 2011ho in NGC 3847 = Psn J11441295+3330581

Report the discovery of an apparent supernova in public images from the Catalina Sky Survey (CSS). SN 2011 UT R.A. (2000.0) Decl. Mag. Offset 2011ho Oct. 28.49 11 44 12.95 +33 30 58.1 18.7 12".8 W, 5".8 N This variable was designated PSN J11441295+3330581 when it was posted on the Central Bureau's TOCP webpage and is here designated SN 2011ho based on the spectroscopic confirmation reported below. Further unfiltered CCD magnitudes for 2011ho: June 11.21 UT, [19.0 (CSS); Oct. 30.495, 18.3 (Joseph Brimacombe, Cairns, Australia; position end figures 13s.10, 59".2; image posted at website URL http://www.flickr.com/photos/43846774@N02/6297040020/). R. J. Foley, Harvard-Smithsonian Center for Astrophysics; and D. Kasen and A. V. Filippenko, University of California, Berkeley, report that a CCD spectrum (range 310-1020 nm), obtained on Oct. 31 UT with the Keck I 10-m telescope (+ LRIS), shows that PSN J11441295+3330581 = SN 2011ho is a type-Ia supernova near maximum brightness. The spectrum exhibits a large Si II 597.2-nm/635.5-nm ratio, indicating a cooler photosphere and a lower luminosity. The spectrum is similar to that of SN 1986G at -3 days (Phillips et al. 1987, PASP 99, 592), but it also resembles spectra of the more typical type-Ia supernovae 1992A and 2004eo at a similar epoch. After removing the recession velocity of 9520 km/s (obtained from the Sloan Digital Sky Survey), the minimum of the Si II 635.5-nm feature is blueshifted by 11700 km/s. G. H. Marion, Harvard-Smithsonian Center for Astrophysics (CfA), on behalf of the CfA Supernova Group, reports that a spectrum (range 340-740 nm) of PSN J11441295+3330581 = 2011ho was obtained on Nov. 3 UT by P. Berlind with the F. L. Whipple Observatory 1.5-m telescope (+ FAST). Cross-correlation with a library of supernova spectra using the "Supernova Identification" code (SNID; Blondin and Tonry 2007, Ap.J. 666, 1024) shows that 2011ho is a 1991bg-like type-Ia supernova near maximum light. Good fits can be found to several templates of normal and 1991bg-like type-Ia supernovae within three days of maximum. The presence of a strong feature from Si II 597.2-nm and the reported brightness of 2011ho are consistent with a subluminous, or 1991bg-like, type-Ia supernova. Using an estimated redshift of z = 0.031829 for NGC 3847 as reported in NED (de Vaucouleurs et al. 1991, RC3.9C), the velocity of the Si II 635.5-nm and 597.2-nm features are estimated to be 10700 km/s and 10500 km/s, respectively....