Electronic Telegram No. 3641 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 2013fa IN NGC 6956 = PSN J20435357+1230517 S. Nakano, Sumoto, Japan, reports the discovery by Koichi Itagaki (Teppo-cho, Yamagata, Japan) of an apparent supernova (mag 16.2) on an unfiltered CCD frame (limiting magnitude 19.0) taken remotely on Aug. 25.547 UT using a 0.50-m f/6.8 reflector at the Takanezawa station, Tochigi-ken. The new object is located at R.A. = 20 43 53.57, Decl. = +12d30'51".7 (equinox 2000.0), which is 2" west and 8" north of the nucleus of the presumed host galaxy, NGC 6956. Nothing is visible at this position on Itagaki's most recent survey image of the same field taken on Aug. 17.555 (limiting mag 17.0). Itagaki has posted his discovery image at the following website URL: http://www.k-itagaki.jp/images/ngc-6956.jpg. The variable was designated PSN J20435357+1230517 when it was posted at the Central Bureau's TOCP webpage and is here designated SN 2013fa based on the spectroscopic confirmation reported below. The type-IIP supernova 2006it also appeared in NGC 6956. Additional CCD magnitudes (unfiltered unless noted otherwise) for 2013fa: Aug. 25.590, V = 16.00, I_c = 15.76 (Seiichiro Kiyota, Kamagaya, Japan; remotely using the iTelescope.net T30 0.5-m telescope at Siding Spring; image posted at URL http://meineko.sakura.ne.jp/ccd/PSN_J20435357+1230517.jpg); 25.761, 15.8 (Toshihide Noguchi, Katori, Chiba-ken, Japan, 0.23-m f/6.3 reflector + BITRAN BT-11E camera; limiting mag 17.0; position end figures 53s.53, 51".5; offset 2".9 west, 8".4 north; UCAC4 reference stars; image posted at http://park8.wakwak.com/~ngc/images/PSNinNGC6956.jpg; communicated by Nakano); 25.923, 16.0 (T. Yusa, Osaki, Japan; remotely using a iTelescope T18 0.32-m f/8 astrograph near Nerpio, Spain; position end figures 53s.55, 52".3; UCAC4 reference stars; limiting magnitude 19.3; image posted at URL http://space.geocities.jp/yusastar77/supernova/PSNinN6959_130826.htm); 26.119, 15.6 (E. Conseil; 0.35-m f/11 Schmidt-Cassegrain Slooh Space Telescope at Mt. Teide, Canary Islands; limiting mag 17.7; image posted at website URL http://www.flickr.com/photos/econseil/9595514951/); 27.610, 16.1 (Joseph Brimacombe, Cairns, Australia; 41-cm RCOS telescope + infrared filter; bandpass > 700 nm; position end figures 53s.57, 52".1; image posted at URL http://www.flickr.com/photos/43846774@N02/9611697319/); 27.856, 15.9 (M. Martignoni, Magnago, Italy; 0.25-m f/10 Schmidt-Cassegrain reflector; position end figures 53s.56, 52".1); 27.988, 15.6 (Gianluca Masi and Francesca Nocentini, remotely using a 43-cm telescope at Ceccano, Italy; position end figures 53s.57, 52".3). Masi and Nocentini add that a low-resolution spectrogram dispersion 3.41 nm/pixel) taken on Aug. 28.842 remotely with a 35.6-cm telescope (+ 100-lines/mm grating) at Ceccano shows a clear Si II absorption around 615 nm, suggesting that 2013fa is a type-Ia supernova. M. Yamanaka, Kyoto University; and K. Takaki, Y. Moritani, and K. S. Kawabata, Hiroshima University, obtained a low-resolution optical spectrogram (range 480-900 nm) of PSN J20435357+1230517 = SN 2013fa on Aug. 26.5 UT with the 1.5-m Kanata telescope (+ HOWPol) at Higashi-Hiroshima Observatory. A comparison with a library of supernova spectra using GELATO (Harutyunyan et al. 2008, A.Ap. 488, 383) suggests that the spectrum is consistent with that of the type-Ia supernova 2007bm at three days after B-band maximum. After correcting for the recession velocity of the host galaxy, the spectrum exhibits absorption lines at 484, 525, 543, 576, 609, 745, and 813-nm, which are identified as an Fe II multiplet, S II 545.4- and 564.0-nm, Si II 597.2- and 635.5-nm, O I 777.4-nm, and the Ca II infrared triplet, respectively. The line velocities of Si II 635.5-nm and the Ca II infrared triplet reach 13000 km/s. NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2013 CBAT 2013 August 29 (CBET 3641) Daniel W. E. Green