Electronic Telegram No. 2985 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 2012I = PSN J02582783+0611253 A. J. Drake, S. G. Djorgovski, M. J. Graham, A. Mahabal, and R. Williams, California Institute of Technology; J. L. Prieto, Princeton University; M. Catelan, Pontificia Universidad Catolica de Chile; E. C. Beshore and S. M. Larson, Lunar and Planetary Laboratory, University of Arizona; and E. Christensen, Gemini Observatory, report the discovery of an apparent supernova in unfiltered Catalina Sky Survey (CSS) images: SN 2012 UT R.A. (2000.0) Decl. Mag. Offset 2012I Jan. 18.17 2 58 27.83 + 6 11 25.3 16.3 1".6 E, 6".4 S The variable was designated PSN J02582783+0611253 when it was posted at the Central Bureau's TOCP webpage and is here designated SN 2012I based on the spectroscopic confirmation reported below. Additional CCD magnitudes for 2012I: 2011 Dec. 31.10 UT, [20.5 (CSS); 2012 Jan. 18.913, 16.4 (Paolo Corelli, Pagnacco, Italy; 0.45-m f/4.5 telescope; position end figures 27s.83, 24".9; limiting mag 17.8; unfiltered); 19.113, 16.4 (Joseph Brimacombe, Cairns, Australia; remotely using a 51-cm RCOS telescope + STL11K camera + luminance filter at New Mexico Skies Observatory near Mayhill, NM, U.S.A.; position end figures 27s.80, 25".2; image posted at the following website URL: http://www.flickr.com/photos/43846774@N02/6727514697/). M. R. Drout, D. Milisavljevic, E. Berger, N. Sanders, and A. M. Soderberg, Harvard University, report on low-dispersion spectra (range 330-850 nm) taken on Jan. 19 UT with the 6.5-m MMT (+ Blue Channel). PSN J02582783+0611253 = SN 2012I is a type-Ia supernova near maximum light. Comparison with a library of supernova spectra using the "Supernova Identification" tool (SNID; Blondin and Tonry 2007, Ap.J., 666, 1024) provides a good match with the normal type-Ia supernova 1994D at four days before maximum. Using the SNID-determined redshift of z = 0.029, the velocity of the Si II 635.5-nm feature is estimated to be approximately 11500 km/s. L. Magill and R. Kotak, Queen's University, Belfast, report that an optical spectrum (range 330-900 nm) of PSN J02582783+0611253 = SN 2012I was obtained at the Isaac Newton Telescope (+ Intermediate Dispersion Spectrograph) on Jan. 19.92 UT. Cross-correlation with a library of supernova spectra using the Supernova Identification tool (SNID; Blondin and Tonry, 2007, Ap.J. 666, 1024) resulted in a best match the normal type-Ia supernova 2002er (Kotak et al. 2005, A.Ap. 436, 1021) at an epoch of -4 days, at a redshift of 0.03. M. Dennefeld, Institut d'Astrophysique de Paris; J. Whitbourne, University of Durham; and S. Benetti, Istituto Nazionale di Astrofisica, report that a spectrum (range 370-730 nm; resolution 0.66 nm) of PSN J02582783+0611253 = SN 2012I was obtained on Jan. 19.76 UT with the Haute-Provence 1.93-m telescope (+ Carelec). Using a library of supernova spectra via GELATO (Harutyunyan et al. 2008, A.Ap. 488, 383; available at URL https://gelato.tng.iac.es/login.cgi), they found a best fit with normal type-Ia supernovae a few days after maximum. Allowing for a galaxy redshift of z = 0.022099 (Stein 1996, A.Ap. Suppl. 116, 203; via NED), the expansion velocity measured from the deep Si II 635.5-nm absorption is 9400 km/s. Nearly 24 hours after this object was posted at the TOCP as noted above, W. Zheng, University of Michigan; J. Vinko, University of Szeged; R. Quimby, IPMU, University of Tokyo; N. Whallon, A. Romadan, C. Wagner, and C. Akerlof, University of Michigan; F. Yuan, Australian National University; J. C. Wheeler and E. Chatzopoulos, University of Texas; and G. H. Marion, Harvard-Smithsonian Center for Astrophysics, on behalf of the ROTSE collaboration, reported the independent discovery of 2012I at mag about 16.6 in unfiltered images taken on Jan. 12.16 UT with the 0.45-m ROTSE-IIIb telescope at McDonald Observatory. They measure 2012I to be located at R.A. = 2h58m27s.8, Decl. = +6o11'25".5 (equinox 2000.0; uncertainty about 1"), adding that there is no apparent host galaxy at this position in a Sloan Digital Sky Survey (SDSS) image; the nearest object in the SDSS image is a faint galaxy with magnitude r' = 19.59 lying 1".1 east and 6".2 north of 2012I. Additional approximate ROTSE magnitudes for 2012I: Jan. 14.07, 16.4; 15.10, 16.2; 18.08, 16.2. They provide a finding chart for 2012I at the following website URL: http://www.rotse.net/rsvp/j025827.8+061126/ROTSE3_J025827.8+061126.jpg. A spectrum, obtained on Jan. 17.15 UT with the 9.2-m Hobby-Eberly Telescope (+ Marcario Low-Resolution Spectrograph) by S. Odewahn, shows that 2012I is a type-Ia supernova near maximum light. The spectrum contains the Si II 635.5-nm line and several other characteristic type-Ia-supernova features. According to SNID (Blondin and Tonry 2007, Ap.J. 666, 1024), the spectrum most resembles to that of SN 1996X (at 1.9 days after maximum) and that of SN 2002bo (at 4.4 days before maximum). The median redshift estimate is z = 0.029. Adopting this redshift, the velocity from the absorption minimum of the Si II 635.5-nm feature is 11000 km/s. The R(Si II) ratio is about 0.35, suggesting a type-Ia supernova in the "Low Velocity Gradient" subclass (Benetti et al. 2005, Ap.J. 623, 1011; Altavilla et al. 2009, Ap.J. 695, 135). NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2012 CBAT 2012 January 21 (CBET 2985) Daniel W. E. Green