[IAUC] CBET 3312: 20121126 : SUPERNOVA 2012gw IN ESO 316-38 = PSN J10100915-3808151

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                                                  Electronic Telegram No. 3312
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)
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SUPERNOVA 2012gw IN ESO 316-38 = PSN J10100915-3808151
     Stuart Parker, Oxford, Canterbury, New Zealand, reports his discovery of
an apparent supernova (red mag 14.8) on a 30-s unfiltered CCD image (limiting
mag 18.5) taken on Oct. 6.706 UT with a 35-cm Celestron C14 reflector (+ ST10
camera) at his Parkdale Observatory in the course of the Backyard Observatory
Supernova Search.  The new object is located at R.A. = 10h10m09s.15, Decl. =
-38d08'05".1 (equinox 2000.0; reference stars from USNO-B and UCAC3
catalogues), which is 4" east and 3" south of the nucleus of the galaxy ESO
316-38.  Nothing is visible at this position on Digitized Sky Survey red and
infrared images (limiting red magnitude > 19).  The variable was designated
PSN J10100915-3808151 when it was posted at the Central Bureau's TOCP webpage
and is here designated SN 2012gw based on the spectroscopic confirmation
reported below.  Additional CCD magnitudes for 2012gw:  July 27.298, [18.5
(Parker); Oct. 10.680, 14.8 (Parker; red unfiltered mag; limiting mag 18.0);
11.768, 16.9 (Joseph Brimacombe, Cairns, Australia; infrared filter,
bandpass > 700 nm; position end figures 09s.13, 05".1; image posted at
website URL http://www.flickr.com/photos/43846774@N02/8078525364/).

     Nidia Morrell, Las Campanas Observatory, Carnegie Supernova Project,
reports that an optical spectrogram (range 368-960 nm) of PSN J10100915-3808151
= SN 2012gw was obtained on Nov. 19.35 UT with the 2.5-m du Pont telescope (+
WFCCD) at Las Campanas.  Inspection of the data reveals that 2012gw is an
evolved type-Ia supernova.  Cross-correlation with a library of supernova
spectra via the Supernova Identification tool (Blondin and Tonry 2007, Ap.J.
666, 1024) yields good matches with a number of normal type-Ia supernovae
between 3 and 7 weeks after maximum light.  From a follow-up observation
performed by the discoverers on Oct. 20, it is known that the object was
already declining then at magnitude 15.2; thus we estimate that the current
age of the event can be constrained at roughly 6 weeks after maximum light.


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                         (C) Copyright 2012 CBAT
2012 November 26                 (CBET 3312)              Daniel W. E. Green