Electronic Telegram No. 909 Central Bureau for Astronomical Telegrams INTERNATIONAL ASTRONOMICAL UNION M.S. 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A. IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions) CBAT@CFA.HARVARD.EDU (science) URL http://cfa-www.harvard.edu/iau/cbat.html SUPERNOVA 2007az J. M. Silverman, R. Chornock, and A. V. Filippenko, University of California, Berkeley, report that inspection of CCD spectra (range 340-920 nm), obtained on Mar. 18 UT with the Keck I 10-m telescope (+ LRIS), shows that the possible supernova near UGC 4378 that was announced on CBET 872 is a type-Ib supernova (hereby designated 2007az). The spectrum shows conspicuous lines of He I (rest 587.6, 667.8, 706.5 nm) and closely resembles the spectrum of SN 1999dn at 10 days after maximum (Matheson et al. 2001, A.J. 121, 1648). The host-galaxy's recession velocity, calculated from narrow emission lines, was found to be 10420 km/s. This is nearly a factor of five larger than the recession velocity of the nearby galaxy UGC 4378 (2230 km/s from Schneider et al. 1992, Ap.J. Suppl. 81, 5). Thus, SN 2007az must reside in a background galaxy. NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2007 CBAT 2007 March 27 (CBET 909) Daniel W. E. Green