Electronic Telegram No. 2254 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 2010bu Further to CBET 2234, A. J. Drake, S. G. Djorgovski, A. Mahabal, M. J. Graham, and R. Williams, California Institute of Technology; J. L. Prieto, Carnegie Observatories; M. Catelan, Pontificia Universidad Catolica de Chile; 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 2010 UT R.A. (2000.0) Decl. Mag. Offset 2010bu Apr. 9.37 15 42 58.38 + 2 16 52.6 16.9 2".2 W, 3".1 S Nothing is visible at this position on a CSS image from Mar. 16.46 UT (limiting mag 18.0). J. M. Silverman, I. K. W. Kleiser, C. V. Griffith, and A. V. Filippenko, University of California, Berkeley, report that inspection of a low signal-to-noise ratio CCD spectrum (range 350-1000 nm), obtained on Apr. 15 UT with the 3-m Shane reflector (+ Kast) at Lick Observatory, shows that 2010bu is a normal type-Ia supernova. Cross-correlation with a library of supernova spectra using the "SuperNova IDentification" code (SNID; Blondin and Tonry 2007, Ap.J. 666, 1024) indicates that 2010bu is within a few days of maximum brightness and is at a redshift of 0.039. NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2010 CBAT 2010 April 20 (CBET 2254) Michael Rudenko