Electronic Telegram No. 2654 Central Bureau for Astronomical Telegrams INTERNATIONAL ASTRONOMICAL UNION CBAT Director: Daniel W. E. Green; Hoffman Lab 209; Harvard University; 20 Oxford St.; Cambridge, MA 02138; U.S.A. e-mail: cbatiau@eps.harvard.edu (alternate cbat@iau.org) URL http://www.cbat.eps.harvard.edu/index.html Prepared using the Tamkin Foundation Computer Network SUPERNOVA 2011ab Z. Kuli, Hungarian Astronomical Association; and K. Sarneczky, Konkoly Observatory, write that they discovered of a possible supernova (mag 19.7) in 37.5-min co-added unfiltered CCD images (limiting mag 21.5) taken on Jan. 30.753 UT with the 0.60-m Schmidt telescope at Konkoly Observatory at Piszkesteto, Hungary. The new object, which appeared at mag 19.3 on an image taken on Feb. 1.733, is located at R.A. = 1h09m52s.97, Decl. = +15d59'43".3 (equinox 2000.0), which is 0".6 east of the center of the presumed host galaxy (whose presumed-SDSS r magnitude is 20.6). No point source is visible at this position on co-added 50-min reference images taken on 2010 Oct. 31 and 2011 Jan. 3 (limiting mag 22.5 on both images). An animated gif showing the variable is posted at http://titan.physx.u-szeged.hu/~sky/poss-sn2.gif. J. Vinko, University of Szeged; J. C. Wheeler and E. Chatzopoulos, University of Texas; and G. H. Marion, Harvard-Smithsonian Center for Astrophysics and University of Texas, report that a spectrum of 2011ab, obtained on Feb. 6.07 UT with the 9.2-m Hobby-Eberly Telescope (+ Marcario Low-Resolution Spectrograph; wavelength range 420-1020 nm) by S. Rostopchyn, shows broad P-Cyg features of H-alpha and H-beta superimposed on a blue continuum, implying that the transient is most likely a type-II supernova. The observed spectrum is well matched by P. Nugent's type-II-P supernova template (http://supernova.lbl.gov/~nugent/nugent_templates.html) at six days after shock breakout, which agrees with the brightening of the transient reported by the discoverers. The redshift estimated from the narrow H-alpha feature from the host galaxy is z = 0.075. At the distance of 308 Mpc, the observed brightness of mag 19.3 corresponds to absolute mag -18.1, although this estimate also contains contribution from the host galaxy. NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2011 CBAT 2011 February 11 (CBET 2654) Daniel W. E. Green