[IAUC] CBET 3146: 20120619 : SUPERNOVA 2012cu IN NGC 4772 = PSN J12532935+0209390

Lun Jun 18 20:24:16 ART 2012

                                                  Electronic Telegram No. 3146
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 2012cu IN NGC 4772 = PSN J12532935+0209390
     Koichi Itagaki, Yamagata, Japan, reports his discovery of an apparent
supernova (mag 16.3) on an unfiltered CCD image (limiting magnitude 19.5)
taken on June 14.559 UT, apparently with a 0.60-m f/5.7 reflector.  The new
object is located at R.A. = 12h53m29s.35, Decl. = +2d09'39".0 (equinox 2000.0;
UCAC3 reference stars), which is 3".1 east and 27".1 south of the nucleus of
NGC 4772.  Nothing was visible at this position on Itagaki's reference image
from 2007 Feb. 25.648 (limiting mag 19.5).  His discovery image is posted at
website URL http://www.k-itagaki.jp/4772.jpg.  The variable was designated
PSN J12532935+0209390 when it was posted at the Central Bureau's TOCP webpage
and is here designated SN 2012cu based on the spectroscopic confirmation
reported below.  Additional CCD magnitudes for 2012cu:  June 14.21, V = 16.4
(S. Howerton, Arkansas City, KS, U.S.A.; independent discovery; position end
figures 29s.26, 36".4); 14.582, 16.2 (T. Noguchi, Chiba-ken, Japan; 0.23-m
f/6.3 Schmidt-Cassegrain reflector + BITRAN BT-11E camera; limiting mag 17.5;
position end figures 29s.36, 39".0; UCAC3 reference stars; communicated by
S. Nakano, Sumoto, Japan); 15.177, 15.8 (L. Elenin, Lyubertsy, Russia; and I.
Molotov, Moscow; taken remotely at the ISON-NM Observatory near Mayhill, NM,
USA, with a 0.45-m f/2.8 telescope; position end figures 29s.36 +/- 0".13,
39".2 +/- 0".16; NOMAD reference stars; limiting mag about 20.3; image posted
at http://spaceobs.org/images/TOCP/PSNJ12532935+0209390-20120615.png); 15.248,
16.5 (Joseph Brimacombe, Cairns, Australia; remotely using a 51-cm RCOS
telescope + luminance filter + STL11K camera at New Mexico Skies Observatory
near Mayhill, NM; position end figures 29s.37, 39".4; image posted at website
URL http://www.flickr.com/photos/43846774@N02/7377711798/).

     G. H. Marion and D. Milisavljevic, Harvard-Smithsonian Center for
Astrophysics (CfA), on behalf of the CfA Supernova Group, report that a
spectrogram (range 340-740 nm) of PSN J12532935+0209390 = 2012cu was obtained
on June 15 UT by K. Rines and S. Wilhelmy with the F. L. Whipple Observatory
1.5-m telescope (+ FAST).  Cross-correlation with a library of supernova
spectra using the "Supernova Identification" code (SNID; Blondin and Tonry
2007, Ap.J. 666, 1024) shows that 2012cu is a type-Ia supernova approaching
maximum brightness.  A good fit is found to the template of the 1999aa-like
type-Ia supernova 2008ds at maximum.  Reasonable fits are also found to
templates from several normal type-Ia supernovae between 3 and 7 days before
maximum.  The spectrum is very red, which is attributed to extinction.  Na I
D is strong, with an equivalent width of 1.73 nm, and C II 658.0-nm is also
strong.  The velocity of Si II 635.5-nm is measured at the absorption minimum
to be approximately 11900 km/s.  An estimated redshift of z = 0.003469 for
NGC 4771 was taken via NED (from de Vaucouleurs et al. 1991, RC3.9C).

     T.-M. Zhang and M.-Y. Lin, National Astronomical Observatories of China
(NAOC); and X.-F. Wang, Tsinghua Center for Astrophysics, Tsinghua University,
report on an optical spectrogram (range 400-700 nm) of PSN J12532935+0209390 =
2012cu that was obtained on June 15.6 UT with the 2.16-m telescope (+ BFOSC)
at the Xinglong Station of NAOC.  The spectrum is consistent with a highly-
reddened type-Ia supernova, at an age of about one week before maximum light.
Adopting a recession velocity 1040 km/s (Tully et al. 2008, Ap.J. 676, 184)
for the host galaxy (NGC 4772), the velocity of the Si II 635.5-nm absorption
feature is measured to be about 11600 km/s.


NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
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                         (C) Copyright 2012 CBAT
2012 June 19                     (CBET 3146)              Daniel W. E. Green