[IAUC] CBET 3227: 20120914 : SUPERNOVA 2012et IN MCG +04-55-47 = PSN J23423882+2705315

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                                                  Electronic Telegram No. 3227
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 2012et IN MCG +04-55-47 = PSN J23423882+2705315
  [Editor's note:  this text replaces that on CBET 3226.]
     D. Rich, Hampden, ME, USA, reports his discovery of an apparent supernova
(mag about 16.9) on unfiltered CCD frames (limiting mag 19.0) taken with a
0.41-m reflector on Sept. 12.057 and 13.171 UT.  The new object is located at
R.A. = 23h42m38s.82, Decl. = +27o05'31".5 (equinox 2000.0), which is about
5".3 east and 0".8 north of the center of MCG +04-55-47.  The variable was
designated PSN J23423882+2705315 when it was posted at the Central Bureau's
TOCP webpage and is here designated SN 2012et based on the spectroscopic
confirmation reported below.  Additional magnitudes for 2012et:  1990 Aug.
29, [20.5 (Palomar red plate via Digital Sky Survey; reported by Rich); 1993
Aug. 13, [21.0 (Palomar blue plate via Digital Sky Survey; reported by Rich);
2012 Aug. 21.127, [19.0 (Rich); Sept. 13.971, R_c = 16.6 (Massimiliano
Martignoni, Magnago, Italy; 25-cm f/10 Schmidt-Cassegrain reflector; position
end figures 38s.93, 30".6).

     M. Dennefeld, Institute d'Astrophysique de Paris and Paris6 University;
A. Pizzella, Padova University; M. Valentini, Liege University; L. Tomasella
and S. Benetti, Istituto Nazionale di Astrofisica, Osservatorio Astronomico
di Padova; and the NEON school (cf. IAUC 7664) students M. Cortes (Spain), N.
Ozel (Belgium), and A. Rajpurohit (France), report that a spectrogram of
PSN J23423882+2705315 = SN 2012et, obtained on Sept. 13.80 UT with the 1.82-m
Copernico telescope (+ Afosc spectrograph; range 350-820 nm, resolution 1.3
nm), suggests that this is a type-Ia supernova.  Adopting for the host galaxy
(MCG +04-55-47) a redshift z = 0.024961 (Saintonge et al. 2008, A.J. 135, 588;
via NED), a comparison with a library of supernova spectra via GELATO
(Harutyuyan et al. 2008, A.Ap. 488, 383) shows that 2012et is a type-Ia event
similar to several type-Ia supernovae at a few days before maximum light.
The expansion velocity measured from the Si II 635.5-nm minimum is about 15000
km/s.


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      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2012 CBAT
2012 September 14                (CBET 3227)              Daniel W. E. Green