Electronic Telegram No. 2745 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 2011dm IN UGC 11861 = PSN J21564159+7317489 Further to CBET 2721, M. Kandrashoff, J. Kelly, S. B. Cenko, W. Li, and A. V. Filippenko report the LOSS discovery of an apparent supernova on unfiltered KAIT images: SN 2011 UT R.A. (2000.0) Decl. Mag. Offset 2011dm June 15.42 21 56 41.59 +73 17 48.9 18.8 73" E, 131" N The object was designated PSN J21564159+7317489 when posted at the Central Bureau's TOCP webpage and is here designated SN 2011dm based on the spectroscopic report below. Additional KAIT magnitudes for 2011dm: 2010 June 8.46 UT, [19.8; 2011 June 18.48, 16.5. Joseph Brimacombe, Cairns, Australia, reports that stacked unfiltered CCD images obtained on June 20.399 UT yield mag 16.4 and position end figures 41s.58, 48".5 for PSN J21564159+7317489 = SN 2011dm. His image is posted at URL http://www.flickr.com/photos/43846774@N02/5855725626/. Federica Luppi reports that stacked CCD images taken on June 20.954 UT with a 0.36-m f/7.9 reflector (+ Bessell R filter) at the Schiaparelli Observatory in Italy yield mag 15.8 and position end figures 41s.62, 48".7 for PSN J21564159+7317489 = SN 2011dm. Nothing is visible at this position on Digitized Sky Survey red, blue, and infrared images from 1987 Apr. 21, 1992 June 1, and 1991 May 4, respectively (no limiting magnitudes provided). Luppi's image is posted at the following website URL: http://www.astrogeo.va.it/pub/TOCP/PSN_U11861.jpg. D. Milisavljevic, J. Thorstensen, and R. Fesen, Dartmouth College, report that low-dispersion optical spectra (range 470-670 nm) of PSN J21564159+7317489 = SN 2011dm, obtained on June 22.5 UT with the 2.4-m Hiltner telescope (+ Modspec) at MDM Observatory, show it to be a type-Ia supernova. Cross-correlation with a library of supernova spectra using the "Supernova Identification" code (SNID; Blondin and Tonry 2007, Ap.J. 666, 1024) shows matches with normal type-Ia events at 3-6 days before maximum light. After correcting for the recessional velocity of its host galaxy (UGC 11861) of 1481 km/s, the velocity of the Si II 635.5-nm feature is estimated to be approximately 13000 km/s. Suppressed blue flux and a relatively strong Na D line suggest a significant amount of extinction toward the supernova. Weak C II 658.0-nm absorption is also visible. NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2011 CBAT 2011 June 23 (CBET 2745) Daniel W. E. Green