Electronic Telegram No. 2234 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 SUPERNOVAE 2010bm AND 2010bn Further to CBET 2225, 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; J. L. Prieto, Carnegie Observatories; E. C. Beshore and S. M. Larson, Lunar and Planetary Laboratory, University of Arizona; and E. Christensen, Gemini Observatory, report the CRTS discovery of two supernovae in unfiltered Catalina Sky Survey (CSS) images: SN 2010 UT R.A. (2000.0) Decl. Mag. Offset 2010bm Apr. 4.32 11 22 04.65 + 9 26 44.5 18.3 -- 2010bn Apr. 5.32 11 44 55.72 - 5 04 44.2 17.2 2".6 W, 3".5 S SN 2010bn was not visible on a CSS image from Mar. 12.33 UT (limiting mag 17.7); the host galaxy of 2010bn is "2dFGRS N114Z227", which has a measured redshift of z = 0.053. SN 2010bm was not visible on a CSS image from Mar. 12.25 (limiting mag 20.0). A spectrogram (range 380-900 nm) of 2010bm was obtained with the SMARTS 1.5-m telescope on Apr. 6.1; cross-correlation with a library of supernova spectra using the "SuperNova IDentification" code (SNID; Blondin and Tonry 2007, Ap.J. 666, 1024) shows 2010bm to be similar to the type-IIP supernova 1999em at five days after maximum light. S. B. Cenko, M. T. Kandrashoff, and A. V. Filippenko, University of California, Berkeley, report that inspection of a CCD spectrum (range 350-1000 nm), obtained Apr. 8 UT with the 3-m Shane reflector (+ Kast) at Lick Observatory, reveals that 2010bm is a type-II supernova; cross- correlation with SNID indicates that it is similar to the type-IIP supernova 2004et at about 10 days after maximum light. A spectrum of 2010bn reveals that it is a type-Ia supernova shortly before maximum light. NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2010 CBAT 2010 April 9 (CBET 2234) Daniel W. E. Green