Electronic Telegram No. 3451
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 2013au
     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; and S. M. Larson and E.
Christensen, Lunar and Planetary Laboratory, University of Arizona, report the
Catalina Real-time Transient Survey discovery of an apparent supernova in
unfiltered Catalina Sky Survey (CSS) images:

 SN       2013 UT       R.A. (2000.0) Decl.       Mag.      Offset
 2013au   Mar. 23.25   12 21 14.16  +47 29 52.4   17.7       1" N

Nothing is visible at this position on a CSS image from Jan. 22.45 UT
(limiting mag 20.5).

     Denis Denisenko, Sternberg Astronomical Institute (SAI), reports the
independent discovery of 2013au at mag 16.8 by P. Balanutsa on 60-s
unfiltered MASTER-Amur survey images (limiting mag 17.9) obtained on Mar.
28.480 UT with 0.40-m f/2.5 reflector.  The position of the variable was given
as R.A. = 12h21m14s.27, +47o29'51".4 (equinox 2000.0), which is 1".8 east and
0".3 south of the center of the faint galaxy SDSS J122114.16+472951.0.
Nothing was visible at this position on an image taken on Feb. 21.693 with
the same telescope to limiting magnitude 18.3.  Denisenko and E. Gorbovskoy
(SAI) find that 2013au was already present at magnitude about 17.7 on
MASTER-Amur images taken on Mar. 21.757 and 25.462, but it was not detected
automatically then.  The MASTER discovery and reference images are available
at website URL http://master.sai.msu.ru/static/OT/122114.27472951.4.png.

     J. Polshaw, R. Kotak, D. Wright, M. Fraser, and S. J. Smartt, Queens
University, Belfast; and A. Lawrence, University of Edinburgh, report that a
spectrogram (range 330-975 nm; resolution about 1000) of 2013au was obtained
on Mar. 30.93 UT with the 4.2-m William Herschel Telescope (+ ISIS).
Cross-correlation with a library of supernova spectra via the "Supernova
Identification" code (SNID; Blondin and Tonry 2007, Ap.J. 666, 1024) shows
that 2013au is a normal type-Ia supernova around maximum light, at a redshift
of z = 0.042.  The presumed host galaxy of 2013au, SDSS J122114.16+472951.0,
has an r' magnitude of 22.2, implying an absolute magnitude for the host of
only -14.2.


NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2013 CBAT
2013 April 2                     (CBET 3451)              Daniel W. E. Green