Electronic Telegram No. 2561 Central Bureau for Astronomical Telegrams INTERNATIONAL ASTRONOMICAL UNION CBAT Director: Daniel W. E. Green; Hoffman Lab 209; Harvard University; 20 Oxford St.; Cambridge, MA 02138; U.S.A. e-mail: cbatiau@eps.harvard.edu (alternate cbat@iau.org) URL http://www.cbat.eps.harvard.edu/index.html Prepared using the Tamkin Foundation Computer Network SUPERNOVA 2010kg IN NGC 1633 [NOTE: This text replaces that on CBET 2560.] Further to CBET 2552, I. Nayak, S. B. Cenko, W. Li, and A. V. Filippenko report the LOSS discovery of an apparent supernova on unfiltered KAIT images: SN 2010 UT R.A. (2000.0) Decl. Mag. Offset 2010kg Nov. 29.34 4 40 08.40 + 7 21 00.0 18.8 10".5 W, 3".0 N Additional KAIT magnitudes for 2010kg: a co-added frame from Sept.-Oct., [20.5; Nov. 30.37 UT, 17.7. G. H. Marion, P. Challis, and R. Kirshner, Harvard-Smithsonian Center for Astrophysics (CfA), on behalf of the CfA Supernova Group, report that a spectrum (range 340-740 nm) of 2010kg was obtained on Dec. 1 UT by M. Calkins 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 2010kg is a type-Ia supernova more than one week before maximum brightness. The velocity of the Si II 635.5-nm feature, measured at the absorption minimum, is about 21200 km/s. NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2010 CBAT 2010 December 3 (CBET 2561) Daniel W. E. Green