Electronic Telegram No. 1731 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 2009bb IN NGC 3278 G. Pignata, J. Maza, M. Hamuy, R. Antezana, L. Gonzalez, P. Gonzalez, P. Lopez, S. Silva, G. Folatelli, D. Iturra, R. Cartier, F. Forster, and S. Marchi, Universidad de Chile; B. Conuel, Wesleyan University; and D. Reichart, K. Ivarsen, A. Crain, D. Foster, M. Nysewander, and A. LaCluyze, University of North Carolina at Chapel Hill, on behalf of the CHASE project, report the discovery of an apparent supernova (mag approximately 17.0 +/- 0.3) on an unfiltered image taken on Mar. 21.11 UT with the 0.41-m 'PROMPT 3' telescope located at Cerro Tololo. The new object, which is also present at mag approximately 16.6 +/- 0.2 in an image taken on Mar. 23.01 , is located at R.A. = 10h31m33s.87 +/- 0".1, Decl. = -39o57'30".0 +/- 0".1 (equinox 2000.0), which is about 17".0 west and 13".5 south of the center of the galaxy NGC 3278. Nothing is visible at this position on template-subtracted archival images taken on Mar. 15.13 (limiting mag 18.5) and Mar. 19.20 (limiting mag 18.0). NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2009 CBAT 2009 March 23 (CBET 1731) Daniel W. E. Green