Electronic Telegram No. 2892 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 2011hk IN NGC 881 = PSN J02184584-0638304 S. Nakano, Sumoto, Japan, reports the discovery by Yoji Hirose (Tsutsumi, Chigasaki, Kanagawa-ken, Japan) of a possible supernova (mag 16.2) on six unfiltered CCD frames (limiting magnitude 17.5) taken around Oct. 31.585 UT using a 0.35-m f/5.7 Schmidt-Cassegrain reflector (+ SBIG ST9XEi camera). The new object is located at R.A. = 2h18m45s.81, Decl. = -6d38'30".5 (equinox 2000.0), which Hirose figured to be 7".5 east and 6".5 south of the center of the galaxy NGC 881 (though he wrote "west"). Nakano also reports the independent discovery of this apparent supernova at mag 16.1 by Koichi Itagaki (Teppo-cho, Yamagata, Japan) on unfiltered CCD frames (limiting magnitude 19.5) taken on Oct. 31.599 with a 0.60-m f/5.7 reflector (+ BITRAN BT-21 camera). Itagaki provides position end figures 45s.84, 30".4 (offset 9".2 east, 9".9 south); Itagaki notes that nothing is visible at this position on the Digitized Sky Survey (limiting mag about 20, but no bandpass or date given). The variable was designated PSN J02184584-0638304 when it was posted by Itagaki on the Central Bureau's TOCP webpage and is here designated SN 2011hk based on the spectroscopic confirmation reported below. Itagaki's discovery image is posted at website URL http://www.k-itagaki.jp/images/ngc-881.jpg. Additional magnitudes for 2011hk (via unfiltered CCD unless noted otherwise): 2006 Aug. 6.766 UT, [19.5 (Itagaki); 2011 Sept. 19, [17 (Hirose); Oct. 18.623, [18.1 (Itagaki); Nov. 1.102, 15.6 (L. Elenin, remotely using a 0.45-m f/2.8 astrograph at the ISON-NM Observatory near Mayhill, NM, USA; position end figures 45s.74, 29".9; NOMAD reference stars; limiting magnitude about 19.5); 1.294, 16.9 (T. Yusa, Osaki, Japan; remotely using a 0.25-m f/3.4 hyperbolic astrograph + SBIG ST-10XME camera, located at the RAS Observatory near Mayhill, NM, U.S.A.; position end figures 45s.79, 30".1; offset 7".9 east, 9".8 south; limiting magnitude = 18.5); 1.356, 17.3 (Joseph Brimacombe, Cairns, Australia; position end figures 45s.78, 31".7; image posted at website URL http://www.flickr.com/photos/43846774@N02/6303839390/); 1.473, 16.9 (T. Noguchi, Katori, Chiba-ken, Japan; 0.23-m f/6.3 Schmidt-Cassegrain reflector + BITRAN BT-11E camera; limiting mag 17.5; position end figures 45s.83, 30".5; UCAC3 reference stars); 2.029, 16.1 (C. Jacques and E. Pimentel, Belo Horizonte, Brazil; remotely using the GRAS G07 telescope near Nerpio, Spain; limiting magnitude 17.5; position end figures 45s.72, 31".0; UCAC2 reference stars; image posted at website URL http://ceamig-rea.net/tocp/n881.jpg). Elenin's image is posted at the following website URL: http://spaceobs.org/images/TOCP/PSNJ02184584-0638304.jpg. G. H. Marion, Harvard-Smithsonian Center for Astrophysics (CfA), on behalf of the CfA Supernova Group, reports that a spectrum (range 340-740 nm) of PSN J02184584-0638304 = 2011hk was obtained on Nov. 1 UT by P. Berlind with the F. L. Whipple Observatory 1.5-m telescope (+ FAST). Cross-correlation with a library of supernova spectra using the "Supernova Identification" code (SNID; Blondin and Tonry 2007, Ap.J. 666, 1024) shows that 2011hk is a 1991bg- like type-Ia supernova a few days after maximum light. The best fit is to a template of SN 1991bg at 3 days post-maximum. Using an estimated redshift of z = 0.0180, as measured from host-galaxy emission lines, the velocity of the Si II 635.5-nm feature is estimated to be approximately 10000 km/s. The Si II 597.2-nm feature is also strong in the spectrum of 2011hk, and the measured velocity for this feature is 9600 km/s. NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2011 CBAT 2011 November 2 (CBET 2892) Daniel W. E. Green