Electronic Telegram No. 1783 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 2009dr Further to CBET 1754, R. Quimby, California Institute of Technology -- together with M. M. Kasliwal, P. Nugent, D. A. Howell, A. Rau, and V. Bhalerao -- on behalf of the larger "Palomar Transient Factory" collaboration, report the discovery of a supernova (R magnitude about 20.3) in multiple images obtained with the Palomar Observatory 1.2-m Oschin Schmidt telescope (+ CFH12K camera) during Apr. 17.25-17.50 UT. Follow-up imaging obtained with the Palomar Observatory 1.5-m telescope shows that the new object, designated 2009dr, brightened to magnitude r = 18.5 on Apr. 28.77. SN 2009dr is located at R.A. = 14h44m42s.08, Decl. = +49o43'44".9 (equinox 2000.0; uncertainty < 1"). No host galaxy is detected in reference data (limiting R mag about 22.7), nor is a source present in the Sloan Digital Sky Survey at this location. Spectra (range 325-1000 nm) of 2009dr, obtained on Apr. 27.37 with the 5.1-m Palomar Hale telescope (+ DBSP), show some similarities to early spectra of SN 2007if (cf. CBET 1059), which later resembled spectra of SN 2003fg. SN 2003fg has been proposed to be a super-Chandrasekhar-mass explosion (Howell et al. 2006, Nature 443, 308). Template matching indicates an approximate redshift of z = 0.1. Additional information was posted at http://www.astronomerstelegram.org/?read=2037. NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2009 CBAT 2009 April 29 (CBET 1783) Daniel W. E. Green