[IAUC] CBET 3303: 20121122 : SUPERNOVA 2012gm IN NGC 7580 = PSN J23173703+1400089

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                                                  Electronic Telegram No. 3303
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 en eps.harvard.edu (alternate cbat en iau.org)
URL http://www.cbat.eps.harvard.edu/index.html
Prepared using the Tamkin Foundation Computer Network


SUPERNOVA 2012gm IN NGC 7580 = PSN J23173703+1400089
     D. Rich, Hampden, ME, USA, reports his discovery of an apparent supernova
(mag about 15.7) on unfiltered CCD frames (limiting mag 19.0) taken with a
0.41-m reflector on Nov. 19.095 and 19.964 UT.  The new object is located at
R.A. = 23h17m37s.03, Decl. = +14o00'08".9 (equinox 2000.0), which is about
9".2 east and 4".6 north of the center of NGC 7580.  The variable was
designated PSN J23173703+1400089 when it was posted at the Central Bureau's
TOCP webpage and is here designated SN 2012gm based on the spectroscopic
confirmation reported below.  Additional magnitudes for 2012gm (obtained via
CCD unless noted otherwise):  1990 Oct. 23, [20.4 (Palomar Digital Sky Survey
red plate); 1992 Sept. 25, [21.0 (Palomar Sky Survey blue plate); 2012 Sept.
24.085, [19.0 (Rich; CCD); Nov. 20.154, V = 15.9 (R. A. Koff, Bennett, CO,
USA; Meade 0.25-m f/10 reflector + Apogee U-47 camera; limiting mag 18.1;
position end figures 37s.02, 08".3; UCAC3 reference stars; image posted at URL
http://antelopehillsobservatory.org/SNpictures/PSNJ23173703+1400089final.jpg);
20.484, V = 16.2 (M. Koishikawa, Sendai Astronomical Observatory, Japan; 1.3-m
f/4.85 reflector; position end figures 37s.15, 09".0; UCAC-3 reference stars);
21.955, 16.5 (Paolo Corelli, Pagnacco, Italy; 0.45-m f/4.5 telescope; position
end figures 37s.05, 09".1).

     P. Ochner, A. Pastorello, S. Benetti, E. Cappellaro, L. Tomasella, and
M. Turatto, Osservatorio Astronomico di Padova, Istituto Nazionale di
Astrofisica; and S. Ciroi, Dipartimento di Fisica e Astronomia, Universita' di
Padova, report that optical spectroscopy (range 340-800 nm; resolution 0.8
nm), obtained on Nov. 21.74 UT with the Asiago 1.22-m Galileo Telescope (+
Boller & Chivens spectrograph) shows that PSN J23173703+1400089 = SN 2012gm
is a type-Ia supernova at redshift z around 0.0148 (Springob et al. 2005,
Ap.J. Suppl. 160, 149; Pertrosian et al. 2007, Ap.J. Suppl. 170, 33; via NED
database).  The best match was found with the type-Ia supernova 2003du
(Stanishev et al. 2007, A.Ap. 469, 645) about one week before its B-band
maximum light.  The expansion velocity of the ejected material, as deduced
from the position of the Si II 635.5-nm absorption, is about 11500 km/s.  The
Asiago classification spectra are posted at 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).


NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
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                         (C) Copyright 2012 CBAT
2012 November 22                 (CBET 3303)              Daniel W. E. Green