Electronic Telegram No. 2560 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 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 2010X1 Nov. 29.34 4 40 08.40 + 7 21 00.0 18.8 10".5 W, 3".0 N Additional KAIT magnitudes for 2010X1: 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at the absorption minimum, is about 21200 km/s. NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars.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 2560) Daniel W. E. Green