Electronic Telegram No. 3570
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 2013dn IN PGC 71942 = PSN J23374574+1442371
     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
 2013dn   June 14.45   23 37 45.74  +14 42 37.1   16.2    1".1 E, 12".8 N

The variable was designated PSN J23374574+1442371 when it was posted at the
Central Bureau's TOCP webpage and is here designated SN 2013dn based on the
spectroscopic confirmation reported below.  Additional CCD magnitudes for
2013dn:  June 15.728 UT, 16.4 (J. Brimacombe, Cairns, Australia; 41-cm
telescope + infrared filter; bandpass > 700 nm; position end figures 45s.82,
36".7; image posted at http://www.flickr.com/photos/43846774@N02/9057732080/);
16.453, 16.4 (Brimacombe; remotely using a 51-cm RCOS telescope + STL11K
camera + luminance filter at the New Mexico Skies observatory near Mayhill,
NM, U.S.A.; position end figures 45s.81, 37".0; image posted at website URL
http://www.flickr.com/photos/43846774@N02/9059433185/); 17.450, 16.4
(Brimacombe; as on June 16; position end figures 45s.79, 36".9; image posted
at website URL http://www.flickr.com/photos/43846774@N02/9072629618/); 21.40,
16.0 (CSS).

     S. Benetti, A. Pastorello, E. Cappellaro, L. Tomasella, P. Ochner, and
M. Turatto, Osservatorio Astronomico di Padova, Istituto Nazionale di
Astrofisica; A. Harutyunyan, Telescopio Nazionale Galileo (TNG); and A. J.
Drake, California Institute of Technology, report that an optical spectrogram
(range 333-965 nm; resolution 1.1 nm) of PSN J23374574+1442371 = SN 2013dn,
obtained on June 26.13 UT with the TNG Telescope (+ Dolores), shows that this
is a type-IIn supernova.  A very good match is found with the type-IIn
supernova 2005gj (Aldering et al. 2006, Ap.J. 650, 210; Prieto et al. 2007,
posted at website URL http://lanl.arxiv.org/abs/0706.4088) at about 54 days
after explosion.  The spectrum is dominated by an H_alpha emission with
complex profile, consisting of a broad component (FWHM about 13000 km/s), an
intermediate one (FWHM about 2200 km/s), and a barely resolved, narrow one.
Given the redshift of the parent galaxy (z about 0.056185, after Strauss
1995, in NSSDC ver. 7185; via NED) and the magnitude at discovery, the
derived absolute magnitude for this event is about -21.1, somewhat brighter
than that derived for SN 2005gj around maximum light.


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      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2013 CBAT
2013 July 1                      (CBET 3570)              Daniel W. E. Green