Electronic Telegram No. 1112 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 2007ob F. Yuan, University of Michigan; R. Quimby, California Institute of Technology; J. Aretakis and C. Akerlof, University of Michigan; and J. C. Wheeler, University of Texas, on behalf of the ROTSE collaboration, report the discovery of a supernova on unfiltered CCD images obtained with the 0.45-m ROTSE-IIIb telescope at McDonald Observatory on Oct. 28.13 (at mag about 17; poor seeing) and 30.23 UT (mag about 17.5); the new object was found by subtracting a co-addition of images taken between July 15 and Aug. 16 (limiting mag about 19.6). SN 2007ob is located at R.A. = 23h12m25s.99, Decl. = +13o54'49".3 (equinox 2000; uncertainty < 1"), which is 0".1 east and 0".7 south of the center of the apparent host galaxy. A finding chart can be found at URL http://www.rotse.net/transients/j2312+1355/index.html. A spectrum (range 420-890 nm) was obtained on Nov. 1.22 with the 9.2-m Hobby-Eberly Telescope (+ Marcario Low-Resolution Spectrograph) by J. Caldwell, V. Riley, and E. Terrazas, and though the data are heavily contaminated by galaxy light, several broad features indicative of a type-Ia supernova are detected: Specifically, an absorption trough is observed around 630 nm, which is identified as Si II 635.5-nm; correcting for the recession velocity using the host-galaxy redshift from the SDSS, the expansion velocity derived from the minimum of this Si II feature is about 12000 km/s. NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2007 CBAT 2007 November 2 (CBET 1112) Daniel W. E. Green