Electronic Telegram No. 2090 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://www.cfa.harvard.edu/iau/cbat.html SUPERNOVA 2009mt Further to CBET 2060, M. Catelan, Pontificia Universidad Catolica de Chile; A. J. Drake, S. G. Djorgovski, A. Mahabal, M. J. Graham, and R. Williams, California Institute of Technology; E. C. Beshore and S. M. Larson, Lunar and Planetary Laboratory, University of Arizona; and E. Christensen, Gemini Observatory, report the CRTS discovery of a supernova in unfiltered Catalina Sky Survey (CSS) images: SN 2009 UT R.A. (2000.0) Decl. Mag. Offset 2009mt Nov. 25.35 4 02 57.68 +17 56 26.7 17.1 1".1 E, 1".3 N Further CSS magnitudes for 2009mt: Nov. 8.30 UT, [20.0; Dec. 11.31, 17.9. A spectrogram (range 380-900 nm) of 2009mt was obtained with the SMARTS 1.5-m telescope on Dec. 19.16; cross-correlation with a library of supernova spectra using the "SuperNova IDentification" code (Blondin and Tonry 2007, Ap.J. 666, 1024) shows 2009mt to be similar to the type-Ia supernova 1996X around four weeks past maximum light. NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2009 CBAT 2009 December 22 (CBET 2090) Daniel W. E. Green