Electronic Telegram No. 3428
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 2013ag
     G. Dhungana, Southern Methodist University; J. M. Silverman, University
of Texas; J. Vinko, University of Szeged; F. V. Ferrante and R. Kehoe,
Southern Methodist University; R. Quimby, Kavli IPMU, University of Tokyo; W.
Zheng, University of California at Berkeley; F. Yuan, Australian National
University; J. C. Wheeler and E. Chatzopoulos, University of Texas; C.
Akerlof, University of Michigan; and G. H. Marion, Harvard-Smithsonian Center
for Astrophysics, on behalf of the ROTSE collaboration, report the discovery
of a supernova (mag about 16.0) in unfiltered images taken on Mar. 2.34 UT
with the 0.45-m ROTSE-IIIb telescope at McDonald Observatory.  The transient
was observed again at similar brightness on Mar. 3.33 UT, with no detection
before Feb. 5 down to a limiting magnitude of about 18.5.  The new object is
located at R.A. = 12h51m35s.02, Decl. = +26o37'45".4 (equinox 2000.0;
uncertainty about 1"), which is 14".9 west and 1".1 north of the presumed host
galaxy (SDSS J125135.41+263744.09), whose SDSS spectroscopic redshift is z =
0.02129+/- 0.00004; a finding chart is posted at the following website URL:
http://www.rotse.net/rsvp/j125135.0+263745/ROTSE3_J125135.0+263745.jpg.
      A spectrogram, obtained on Mar. 3.26 UT with the 9.2-m Hobby-Eberly
Telescope (+ Marcario Low-Resolution Spectrograph) by S. Rostopchin, shows
that 2013ag is a high-velocity type-Ia supernova (Wang et al. 2009, Ap.J. 699,
L139).  Correlation with a library of supernova spectra using the "SuperNova
IDentification" code (SNID; Blondin and Tonry 2007, Ap.J. 666, 1024) indicates
that 2013ag is about 2 days before maximum brightness and spectroscopically
similar to the the high-velocity type-Ia supernova 2002bo (Benetti et al. 2004,
MNRAS 348, 261).  After removal of the host-galaxy recession velocity of 6387
km/s (via SDSS DR7), the absorption minimum of the Si II 635.5-nm line is
found to be blueshifted by about 12600 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      superseded by text appearing later in the printed IAU Circulars.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 March 4                     (CBET 3428)              Daniel W. E. Green