Electronic Telegram No. 3578 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 2013dt IN NGC 7367 = PSN J22443560+0338380 Stuart Parker, Canterbury, New Zealand, reports the discovery of an apparent supernova (red mag 16.8) on a 30-s unfiltered CCD image (limiting mag 18) taken by himself on June 30.704 UT with a 30-cm Astro-Tech AT12RC Ritchey-Chretien astrograph (+ ST10 camera) at his Parkdale Observatory in the course of the Backyard Observatory Supernova Search. The new object is located at R.A. = 22h44m35s.60, Decl. = +3d38'38".0 (equinox 2000.0; reference stars from USNO-B and UCAC3 catalogues), which is 18" east and 9" north of the nucleus of the galaxy NGC 7367. Nothing is visible at this position on Digitized Sky Survey red and infrared images (limiting red magnitude > 19). Parker has posted an image of the variable at URL http://tinyurl.com/k3mnxln. A confirming image taken by Roberto Volsa on July 2 has been posted at website URL http://www.flickr.com/photos/68799376@N08/9186360633/. The variable was designated PSN J22443560+0338380 when it was posted at the Central Bureau's TOCP webpage and is here designated SN 2013dt based on the spectroscopic confirmation reported below. Additional CCD magnitudes for 2013dt: July 2.697, 16.9 (Joseph Brimacombe, Cairns, Australia; 41-cm telescope + infrared filter; bandpass > 700 nm; position end figures 35s.34, 37".4; image posted at website URL http://www.flickr.com/photos/43846774@N02/9195895135/); 3.111, 16.2 (Parker); 5.081, V = 16.7 (Massimiliano Martignoni, Magnago, Italy; 25-cm Schmidt-Cassegrain reflector; position end figures 35s.60, 36".6); 7.050, R = 15.7 (Xavier Bros, Ager, Spain; 35-cm telescope; position end figures 35s.36, 36".8; image posted at URL http://www.anysllum.com/PSN_NGC7367.jpg); 9.982 and 10.010, 16.5 (S. Shurpakov, 0.40-m f/2.5 MASTER-Kislovodsk robotic telescope; limiting mag 18.6; position end figures 35s.34, 37".4; communicated by V. Lipunov, Sternberg Astronomical Institute; reported as an independent discovery and assigned the designation PSN J22443534+0338374 when posted on the TOCP). L. Tomasella, S. Benetti, A. Pastorello, E. Cappellaro, P. Ochner, and M. Turatto, report that optical spectroscopy (range 340-820 nm; resolution 1.3 nm), obtained on July 2.97 UT with the Asiago 1.82-m Copernico Telescope (+ AFOSC), shows that PSN J22443560+0338380 = SN 2013dt is a type-Ia supernova. Assuming for the host galaxy, NGC 7367, the redshift z = 0.024133 (after de Vaucouleurs et al. 1991, RC3.9; via NED), a good match is found with type-Ia supernovae at a few days before maximun light. The expansion velocity, as deduced from the position of the minimum of the Si II 635.5-nm absorption, is about 11200 km/s. The Asiago classification spectra are posted at website URL http://sngroup.oapd.inaf.it; classification was made via GELATO (Harutyunyan et al. 2008, A.Ap. 488, 383) and SNID (Blondin and Tonry 2007, Ap.J. 666, 1024). NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2013 CBAT 2013 July 10 (CBET 3578) Daniel W. E. Green