Electronic Telegram No. 3509 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 2013cb = PSN J11350174+1607168 Tianmeng Zhang and Xu Zhou, National Astronomical Observatories of China (NAOC); and Xiaofeng Wang and Juncheng Chen, Tsinghua University (THU), China, report the discovery of an apparent supernova (mag 18.1) on unfiltered CCD images taken on May 1.51 UT using the 0.6-m NAOC Schmidt telescope in the course of THU-NAOC Transient Survey (TNTS). The new object is located at R.A. = 11h35m01s.74, Decl. = +16d07'16".8 (equinox 2000.0), which is 2".4 west and 4".8 south of the center of the galaxy SDSS J113501.95+160712.2. Nothing is visible at this position on a Digitized Sky Survey image (no bandpass or limiting magnitude provided). The TNTS images are posted at website URL: http://www.thca.tsinghua.edu.cn/~wangxf/TNTS/PSNJ11350174+1607168.png. The variable was designated PSN J11350174+1607168 when it was posted at the Central Bureau's TOCP webpage and is here designated SN 2013cb based on the spectroscopic confirmation reported below. Additional CCD magnitudes for 2013cb: Apr. 18.5, [20.0 (TNTS); May 3.162, 18.3 (R. A. Koff, Bennett, CO, USA; Meade 0.25-m f/10 reflector + Apogee U-47 camera; limiting mag 20.6; position end figures 01s.71, 14".3; UCAC3 reference stars); 3.209, 17.4 (Joseph Brimacombe, Cairns, Australia; remotely with a 51-cm RCOS telescope + luminance filter at the New Mexico Skies observatory near Mayhill, NM, U.S.A.; position end figures 01s.80, 14".6; image posted at website URL http://www.flickr.com/photos/43846774@N02/8706480644/). L. Tomasella, A. Pastorello, P. Ochner, S. Benetti, E. Cappellaro, and M. Turatto, Osservatorio Astronomico di Padova, Istituto Nazionale di Astrofisica, report that optical spectroscopy (range 340-820 nm; resolution 1.3 nm), obtained on May 4.86 UT with the Asiago 1.82-m Copernico Telescope (+ AFOSC), shows that PSN J11350174+1607168 = SN 2013cb is a type-Ia supernova at redshift z about 0.054127 (SDSS Release 6, 2007; via NED). A good match is found with several normal type-Ia supernovae about a week before maximum light. The expansion velocity, as deduced from the position of the minimum of the Si II 635.5-nm absorption, is about 13000 km/s. The Asiago classification spectra are posted at website URL http://graspa.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). Jinghua Gao, Kaicheng Zhang, and Xiaofeng Wang, Tsinghua University; and Tianmeng Zhang, NAOC, report on an optical spectrogram (range 350-800 nm) of PSN J11350174+1607168 = SN 2013cb that was obtained on May 3.7 UT with the 2.16-m telescope (+ BFOSC) at the Xinglong Station of the NAOC. The spectrum is consistent with a type-Ia supernova a few days after maximum light. Cross-correlation with a library of supernova spectra using the "Supernova Identification" code (SNID; Blondin and Tonry 2007, Ap.J. 666, 1024) shows that 2013cb matches with SN 2006le at -9 days. Adopting a redshift of 0.051 for the presumed host galaxy (from the SNID fit), they measure the velocity of the Si II 635.5-nm absorption feature to be about 13500 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 May 10 (CBET 3509) Daniel W. E. Green