Electronic Telegram No. 2683 Central Bureau for Astronomical Telegrams INTERNATIONAL ASTRONOMICAL UNION CBAT Director: Daniel W. E. Green; Hoffman Lab 209; Harvard University; 20 Oxford St.; Cambridge, MA 02138; U.S.A. e-mail: cbatiau@eps.harvard.edu (alternate cbat@iau.org) URL http://www.cbat.eps.harvard.edu/index.html Prepared using the Tamkin Foundation Computer Network SUPERNOVA 2011bb = PSN J11352709-3800549 G. Pignata and M. Cifuentes, Universidad Andres Bello; J. Maza, M. Hamuy, R. Antezana, L. Gonzalez, R. Cartier, F. Forster, S. Silva, F. Carrasco, P. Sanchez, and C. Hervias, Universidad de Chile; B. Conuel, Wesleyan University; G. Folatelli, IPMU, University of Tokyo; 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 (which is part of the Millennium Center for Supernova Science collaboration), report the discovery of an apparent supernova (mag approximately 16.6) on an unfiltered image taken on Mar. 14.08 UT with the 0.41-m 'PROMPT 1' telescope located at Cerro Tololo. The new object, which is also present at mag approximately 17.0 in an image taken on Mar. 8.18, is located at R.A. = 11h35m27s.09 +/- 0".3, Decl. = -38o00'54".9 +/- 0".3 (equinox 2000.0), which is about 2".6 east and 0".7 north of center of the presumed host galaxy. Nothing is visible at this position on archival images taken on Feb. 28.15 (limiting mag 17.5) and Feb. 20.15 (limiting mag 18.0). The variable was designated PSN J11352709-3800549 when posted at the Central Bureau's TOCP webpage and is here designated SN 2011bb based on the spectroscopic report below. J. Anderson and F. Forster, Universidad de Chile; and G. Pignata, Universidad Andres Bello, on behalf of the Millennium Center for Supernova Science, report on an optical spectrogram (range 355-896 nm) of PSN J11352709-3800549 = SN 2011bb that was obtained on Mar. 28.07 UT with the SOAR telescope (+ Goodman HTS). The spectrum shows 2011bb to be a type-Ia supernova at about two weeks after maximum light. Cross-correlation with a library of supernova spectra using the "Supernova Identification" code (SNID; Blondin and Tonry 2007, Ap.J. 666, 1024) provides good matches with SN 1995D at +14 days. NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2011 CBAT 2011 April 7 (CBET 2683) Daniel W. E. Green