Electronic Telegram No. 2684
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@eps.harvard.edu (alternate cbat@iau.org)
URL http://www.cbat.eps.harvard.edu/index.html
Prepared using the Tamkin Foundation Computer Network


SUPERNOVA 2011bc IN NGC 4076 = PSN J12043294+2012114
     Ron Arbour, South Wonston, Hants, U.K., reports his discovery of an
apparent supernova (mag 17.3) on unfiltered CCD images (limiting mag 18.8)
taken on Apr. 1.9579 UT using a 35-cm f/6 Schmidt-Cassegrain telescope (+
Starlight Xpress CCD camera) in the course of his supernova patrol.
The new object (which was designated PSN J12043294+2012114 when posted on the
Central Bureau's TOCP webpage and is here designated SN 2011bc based on the
spectroscopic reports below) is located at R.A. = 12h04m32s.94, Decl. =
+20d12'11".4 (equinox 2000.0), which is 5".8 east and 6".5 south of the
center of the galaxy NGC 4076.  Nothing is visible at this position on the
Digitized Sky Survey blue plate from 1990 Mar. 22 or the red plate from
1997 Mar. 9 (limiting mag about 20.0).
     Additional unfiltered CCD magnitudes for PSN J12043294+2012114 =
SN 2011bc:  2007 Feb. 24.690 UT, [19.5 (K. Itagaki, Yamagata, Japan;
communicated by S. Nakano, Sumoto); 2011 Mar. 31.638, 18.5 (Itagaki;
pre-discovery observation; position end figures 32s.96, 11".6; communicated by
Nakano); Apr. 3.172, 17.9 (Joseph Brimacombe, Cairns, Australia; remotely
using a 51-cm RCOS telescope + STL11K camera at New Mexico Skies Observatory,
Mayhill, NM, U.S.A.; position end figures 32s.98, 10".6); 3.691, 16.7 (N.
Kojima, Aichi, Japan, 0.25-m f/6.3 Schmidt-Cassegrain reflector; position end
figures 32s.93, 11".9; offset 6" east, 6" south; independent discovery;
communicated by Nakano).  Brimacombe has posted his image at the following
website URL:  http://www.flickr.com/photos/43846774@N02/5584270215/.  Itagaki
has posted his images at http://www.k-itagaki.jp/images/4076.jpg.
     The type-Ia supernova 2007M also appeared in NGC 4076 (cf. CBET 816).

     G. H. Marion, Harvard-Smithsonian Center for Astrophysics (CfA), on
behalf of the CfA Supernova Group, reports that a spectrum (range 340-740 nm)
of PSN J12043294+2012114 = 2011bc was obtained on Apr. 3 UT by Marion 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 the object is a
type-Ia supernova several days before maximum light.  Using the NED redshift
of z = 0.020728 for NGC 4076 (which is the presumed host), they estimate the
velocity of the Si II 635.5-nm feature to be approximately 17000 km/s.

     D. D. Balam, Dominion Astrophysical Observatory, National Research
Council of Canada (NRCC); M. L. Graham, Las Cumbres Observatory Global
Telescope, University of California at Santa Barbara; E. Y. Hsiao, Lawrence
Berkeley Laboratory; G. Sarty, University of Saskatchewan; and D. W. E. Green,
Harvard University, report that a spectrogram (range 361-670 nm, resolution
0.3 nm) of PSN J12043294+2012114 = SN 2011bc, obtained on Apr. 7.34 UT with
the 1.82-m Plaskett Telescope of the NRCC, shows it to be a type-Ia supernova
before maximum light.  Cross-correlation with a library of supernova spectra
using the "Supernova Identification" code (Blondin and Tonry 2007, Ap.J. 666,
1024) indicates that 2011bc is most similar to the type-Ia supernova 1999ee
at one week before maximum light.


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

                         (C) Copyright 2011 CBAT
2011 April 7                     (CBET 2684)              Daniel W. E. Green