Electronic Telegram No. 2229 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 2010bi IN NGC 3509 G. Pignata and M. Cifuentes, Universidad Andres Bello; J. Maza, M. Hamuy, R. Antezana, L. Gonzalez, P. Gonzalez, S. Silva, G. Folatelli, R. Cartier, F. Forster, S. Marchi, and A. Rojas, Universidad de Chile; B. Conuel, Wesleyan University; and D. Reichart, K. Ivarsen, J. Haislip, 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 17.7 +/- 0.4) on an unfiltered image taken on Mar. 24.16 UT with the 0.41-m 'PROMPT 5' telescope located at Cerro Tololo. The new object, which is also present in an image taken on Mar. 25.13 at mag approximately 17.7, is located at R.A. = 11h04m25s.49 +/- 0".1, Decl. = +4o50'17".6 +/- 0".1 (equinox 2000), which is about 28".4 east and 34".6 north of the center of the galaxy NGC 3509. Nothing is visible at this position on archival images taken on Feb. 22.25 (limiting mag 18.0) and on a stack of 21 archival images taken between 2008 Dec. 6.32 and 2010 Feb. 22.25 (limiting mag 20.5). NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2010 CBAT 2010 March 25 (CBET 2229) Daniel W. E. Green