Electronic Telegram No. 116 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://cfa-www.harvard.edu/iau/cbat.html SUPERNOVA 2005ap R. Quimby, P. Mondol, P. Hoeflich, and J. C. Wheeler, University of Texas; and C. Gerardy, Imperial College, report the discovery of an apparent supernova (mag about 18.5) in unfiltered CCD images taken on Mar. 3.30 and 4.29 UT using the 0.45-m ROTSE-IIIb telescope at the McDonald Observatory. The new object is located at R.A. = 13h01m14s.84, Dec. = +27o43'31".4 (equinox 2000.0), which is 3".5 west and 3".4 north of the apparent host galaxy. ROTSE-IIIb co-added images taken between 2004 Dec. 15 and 2005 Jan. 14 (limiting mag about 18.8) show nothing at this position; there is clearly a new point source that is absent on the Digitized Sky Survey. A spectrum (range 430-890 nm) of SN 2005ap, obtained on Mar. 7.46 with the 9.2-m Hobby/Eberly Telescope (+ Marcario Low-Resolution Spectrograph) by B. Roman and V. Riley, shows a flat continuum with broad absorption at 526 and 557 nm, and there are no features that would suggest a Galactic source. The spectrum is similar to the recent CfA spectrum of 2005an (cf. IAUC 8491), but of higher S/N; as with 2005an, Quimby et al. believe that SN 2005ap is an early type-II supernova, but given the general lack of distinct features, they cannot associate it with a template. NOTE: These 'Central Bureau Electronic Telegrams' are intended to be preliminary announcements of items that later appear in the formal IAU Circulars. Citations should normally be made to IAUCs rather than to CBETs. (C) Copyright 2005 CBAT 2005 March 8 (CBET 116) Daniel W. E. Green