[IAUC] CBET 2946: 20111221 : SUPERNOVA 2011ja IN NGC 4945 = PSN J13051112-4931270

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                                                  Electronic Telegram No. 2946
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 2011ja IN NGC 4945 = PSN J13051112-4931270
     L. A. G. Monard, Calitzdorp, Western Cape, South Africa, reports his
discovery of an apparent supernova (magnitude 14.0) on unfiltered CCD taken at
the Klein Karoo Observatory on Dec. 18.086 UT.  The new object is located at
R.A. = 13h05m11s.09 +/- 0s.03, Decl. = -49d31'27".1 +/- 0".1 (equinox 2000.0;
UCAC2 reference stars), which is 152" west and about 200" south of the core of
the nearby SBcd-type galaxy NGC 4945 (note that the core of this late-type
galaxy is not well-defined, which makes offset measurements difficult).
Nothing is visible at this position in Digitized Sky Survey images (limiting
red mag 20.5) or on earlier images taken by Monard (limiting mag 18.5 and
deeper).  The variable was designated PSN J13051112-4931270 when it was posted
at the Central Bureau's TOCP webpage and is here designated SN 2011ja based on
the spectroscopic confirmation reported below.  Additional CCD magnitudes
reported for 2011ja:  Nov. 28.091, [17.5 (Monard); Dec. 19.081, 13.9 (Monard);
20.751, 12.3 (Joseph Brimacombe, Cairns, Australia; 41-cm telescope + STL6K
camera + infrared filter; range > 700 nm; position end figures 11s.13, 26".9;
image posted at URL http://www.flickr.com/photos/43846774@N02/6546296733/).

     D. Milisavljevic, Harvard-Smithsonian Center for Astrophysics (CfA); R.
Fesen, Dartmouth College; T. Pickering and E. Romero-Colmenero, South African
Astronomical Observatory and Southern African Large Telescope; and Alicia
Soderberg and Raffaella Margutti, CfA, report that low-dispersion spectra
(range 350-880 nm), obtained on Dec. 19.1 UT during morning twilight with the
10-m SALT telescope (+ RSS), show PSN J13051112-4931270 = SN 2011ja to be a
relatively young type-II 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 reasonable match to the type-IIP event
SN 2004et about a week after maximum light.  After removal of the host-galaxy
recession velocity of 460 km/s (determined from narrow emission lines), the
absorption minimum of the H-alpha line is found to be blueshifted by about
-11000 km/s.  A suppressed blue continuum and noticeable absorption around
Na I are suggestive of significant internal extinction.

     M. Turatto, S. Benetti, A. Pastorello, S. Valenti, F. Bufano, and L.
Tomasella, Istituto Nazionale di Astrofisica, Osservatorio Astronomico di
Padova, on behalf of a larger collaboration, report that a spectrogram of PSN
J13051112-4931270 = SN 2011ja, obtained on Dec. 19.31 UT with the European
Southern Observatory's New Technology Telescope (+ EFOSC2; range 365-930 nm;
resolution 1.8 nm), shows it to be a type-II supernova.  The best fit to this
spectrum found by GELATO (Harutyunyan et al. 2008, A.Ap. 488, 383; available
at website URL https://gelato.tng.iac.es/login.cgi) suggests that 2011ja is
similar to type-II supernovae a few days after explosion, if a redshift of
0.001878 for the host galaxy (Koribalski et al. 2004, A.J. 128, 16; via NED)
and a total reddening of E(B-V) > 1.2 are assumed.  Together with H lines
with broad P-Cyg profiles, absorptions of Fe II, Ca II, and He I are clearly
detected.

     S. Ryder, Australian Astronomical Observatory; A. Soderberg, Harvard
University; C. Stockdale, Marquette University; S. Van Dyk, Spitzer Science
Center, California Institute of Technology; S. Immler, Goddard Space Flight
Center; K. Weiler, Naval Research Laboratory; and N. Panagia, Space Telescope
Science Institute and Observatory of Catania, report the detection of radio
emission near the position of SN 2011ja with the Australia Telescope Compact
Array radio telescope, confirming its core-collapse nature.  A flux density
of 0.44 +/- 0.20 mJy was measured at 18.0 GHz on Dec 19.9 UT.  The measured
position of the radio emission of R.A. = 13h05m11s.06, Decl. = -49o31'26".0
(equinox 2000.0) is in good agreement with the measured optical position (end
figures 11s.12, 27".0).  Radio observations of this nearby (4 Mpc, from NED)
supernova at the Australia Telescope Compact Array are continuing.


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                         (C) Copyright 2011 CBAT
2011 December 21                 (CBET 2946)              Daniel W. E. Green