Electronic Telegram No. 1744 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 2009bx A. J. Drake, S. G. Djorgovski, R. Williams, A. Mahabal, and M. J. Graham, California Institute of Technology; M. Catelan, Pontificia Universidad Catolica; E. C. Beshore, S. M. Larson, and R. Hill, Lunar and Planetary Laboratory, University of Arizona; and E. Christensen, Gemini Observatory, report the CRTS (cf. CBETs 1693, 1713, 1733) discovery of an apparent supernova in unfiltered Catalina Sky Survey (CSS) images: SN 2009 UT R.A. (2000.0) Decl. Mag. Offset 2009bx Feb. 16.37 10 09 10.10 + 7 54 34.4 18.7 1".3 W, 0".5 N Further magnitudes for 2009bx, in part from CCD images taken by the authors with the Palomar 1.52-m reflector (+ Gunn filters) and in part by A. Moskvitin (Special Astrophysical Observatory, presumably with the 1.02-m Zeiss telescope): Jan. 17.53 UT, [20.4 (CSS); Feb. 20.15, g = 18.8, r = 18.6; Feb. 27.84, B = 18.8 +/- 0.2, V = 18.9 +/- 0.1, R = 18.45 +/- 0.23 (Moskvitin); Mar. 17.25, 19.4 (CSS). The faint host galaxy, SDSS J100910.19+075433.9, has Gunn magnitudes > 21. NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2009 CBAT 2009 March 29 (CBET 1744) Daniel W. E. Green