Electronic Telegram No. 2386 Central Bureau for Astronomical Telegrams INTERNATIONAL ASTRONOMICAL UNION CBAT Director: Daniel W. E. Green; Room 209; Dept. of Earth and Planetary Sciences; Harvard University; 20 Oxford St.; Cambridge, MA 02138; U.S.A. e-mail: cbat@iau.org; cbatiau@eps.harvard.edu URL http://www.cfa.harvard.edu/iau/cbat.html SUPERNOVA 2010gn J. Vinko, University of Szeged; G. H. Marion, Harvard-Smithsonian Center for Astrophysics and University of Texas; and J. C. Wheeler, University of Texas, report that the possible supernova reported on CBET 2385 is indeed a type-Ia supernova. A spectrum, obtained on July 21.28 UT with the 9.2-m Hobby-Eberly Telescope (+ Marcario Low-Resolution Spectrograph) by S. Rostopchin, shows broad features of Si II, S II, Fe II, and Ca II, characteristic of type-Ia supernovae near maximum. According to SNID (Blondin and Tonry 2007, Ap.J. 666, 1024), the best resembling template spectrum is that of SN 1996X, about one week after maximum light. The median redshift estimated by SNID is z = 0.0365 +/- 0.0058. Adopting this redshift value, the expansion velocity, from the absorption minimum of the Si II 635.5-nm feature, is 11500 km/s. NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars.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 July 21 (CBET 2386) Daniel W. E. Green