[IAUC] CBET 2847: 20111001 : SUPERNOVA 2011gm IN NGC 644 = PSN J01385459-4235088

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                                                  Electronic Telegram No. 2847
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 2011gm IN NGC 644 = PSN J01385459-4235088
     Colin Drescher, Calamvale, Queensland, Australia, reports the discovery
by Stuart Parker (Oxford, Canterbury, New Zealand) of an apparent supernova
(red mag 15.8, as measured by Drescher) on 30-s unfiltered CCD images taken on
Sept. 21.543 and 21.544 UT with a 35-cm f/6.3 Celestron C14 Schmidt-Cassegrain
reflector (+ ST10 camera).  The new object is located at R.A. = 1h38m54s.59,
Decl. = -42d35'08".8 (equinox 2000.0), which is 18" east and 2" south of the
nucleus of the galaxy NGC 644 (as measured by Drescher).  The variable was
designated PSN J01385459-4235088 when it was posted on the Central Bureau's
TOCP webpage and is here designated SN 2011gm based on the spectroscopic
confirmation reported below.  Additional CCD magnitudes for 2011gm, unfiltered
unless noted otherwise:  Aug. 22.655, [19.4 (Parker); Sept. 23.384, 15.8
(Parker; position end figures 54s.57, 08".9; measured by Drescher); 23.614, R
= 15.8 (Joseph Brimacombe, Cairns, Australia; position end figures 54s.56,
08".8); 23.760, 15.6 (Brimacombe; infrared filter, > 700 nm; position end
figures 54s.58, 08".1); 24.613, 15.6 (Brimacombe; infrared filter); 25.586,
15.7 (C. Jacques and E. Pimentel, Belo Horizonte, Brazil; imaged with a GRAS
telescope at Officer, Australia; limiting magnitude 18.0; position end figures
54s.59, 08".7, UCAC2 reference stars).  Brimacombe's image from Sept. 23.6 is
posted at website URL http://www.flickr.com/photos/43846774@N02/6176674798/.
Brimacombe's image from Sept. 24 is posted at the following website URL:
http://www.flickr.com/photos/43846774@N02/6194733505/.

     D. Milisavljevic, Harvard-Smithsonian Center for Astrophysics; R. Fesen,
Dartmouth College; and T. Pickering and A. Gulbis, South African Astronomical
Observatory, report that low-dispersion spectra (range 320-900 nm) obtained
on Sept. 25.9 UT with the 10-m SALT telescope (+ RSS), show PSN
J01385459-4235088 = SN 2011gm to be a type-Ia supernova.  Cross-correlation
with a library of supernova spectra using the "Supernova Identification" code
(SNID; Blondin and Tonry 2007, Ap.J. 666, 1024) shows a good match to the
normal type-Ia supernova 1994D at two days after maximum light.  After
correcting for the recession velocity 6231 km/s (Mathewson et al. 1992, Ap.J.
Suppl. 81, 413) of its host galaxy (NGC 644), the velocity of the Si II
635.5-nm feature is estimated to be approximately 10600 km/s.


NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
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                         (C) Copyright 2011 CBAT
2011 October 1                   (CBET 2847)              Daniel W. E. Green