[IAUC] CBET 3217: 20120912 : SUPERNOVA 2012em IN PGC 69614 = PSN J22440166+1551493

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                                                  Electronic Telegram No. 3217
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 2012em IN PGC 69614 = PSN J22440166+1551493
     H. Mikuz, Crni Vrh Observatory, reports the discovery by Blaz Mikuz at
Crni Vrh Observatory of an apparent supernova (mag 18.3) on four unfiltered
CCD images (bandpass roughly equivalent to the R band) taken during Sept.
9.895-9.935 UT with the 60-cm f/3.3 Cichocki reflector in the course of the
Comet and Asteroid Search Program (PIKA).  The object is located at R.A. =
22h44m01s.66, Decl. = +15d51'49".3 (equinox 2000.0), which is 14" west and
29" south of the center of PGC 69614; the discovery image is posted at URL
http://www.observatorij.org/vstars/PSN20120909/PSNJ22440166+1551493.jpg.
Nothing is visible at this position on archival PIKA images obtained on six
nights between 2005 June 16 and 2011 Aug. 2 (limiting mag about 19.0-19.5)
or on several Digitized Sky Survey red and blue images from the Palomar Sky
Survey.  The variable was designated PSN J22440166+1551493 when it was posted
at the Central Bureau's TOCP webpage and is here designated SN 2012em based on
the spectroscopic confirmation reported below.  Additional CCD magnitudes for
2012em:  Sept. 10.891, R = 17.9 +/- 0.3 (J. Vales and S. Maticic; 60-cm f/3.3
Cichocki telescope at Crni Vrh Observatory; communicated by B. Mikuz); 11.185,
18.2 (R. A. Koff, Bennett, CO, USA; Meade 0.25-m f/10 reflector + Apogee U-47
camera; limiting magnitude 19.5; position end figures 01s.68, 49".8; UCAC3
reference stars); 11.387, 17.7 (L. Elenin, Lyubertsy, Russia; and I. Molotov,
Moscow, Russia; remotely taken with a 0.45-m f/2.8 telescope located at the
ISON-NM Observatory near Mayhill, NM, USA; position end figures 01s.67 +/-
0".1, 49".6 +/- 0".2; NOMAD reference stars; limiting mag about 19.1).

     F. Taddia, Stockholm University, reports on optical spectroscopy of PSN
J22440166+1551493 = SN 2012em, which was obtained with the Nordic Optical
Telescope (+ ALFOSC; range 350-900 nm, resolution 0.8 nm) on Sept. 11.1 UT.
Cross-correlation of the spectrum with a library of supernova spectra using
the "Supernova Identification" code (Blondin and Tonry 2007, Ap.J. 666, 1024)
shows 2012em to be most similar to the type-Ia supernova 1991bg close to
maximum light.

     S. Benetti, L. Tomasella, E. Cappellaro, A. Pastorello, M. Turatto, and
S. Valenti, Osservatorio Astronomico di Padova, Istituto Nazionale di
Astrofisica, report that a spectrogram of PSN J22440166+1551493 = SN 2012em,
obtained on Sept. 10.95 UT with the 1.82-m Copernico telescope (+ Afosc
spectrograph; range 350-820 nm, resolution 1.3 nm), shows it to be a
peculiar type-Ia supernova.  Adopting for the host galaxy (PGC 69614) a
redshift z = 0.038073 (Kochanek et al. 2001, Ap.J. 560, 566; via NED),
comparison with a library of supernova spectra via GELATO (Harutyuyan et al.
2008, A.Ap. 488, 383) shows that 2012em is a type-Ia event similar to
several sub-luminous type-Ia supernovae (1991bg-like) around maximum light.
The expansion velocity measured from the Si II 635.5-nm minimum is about
10100 km/s.


NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
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                         (C) Copyright 2012 CBAT
2012 September 12                (CBET 3217)              Daniel W. E. Green