Electronic Telegram No. 2868
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 2011gv IN IC 4901 = PSN J19542142-5842390
     Greg Bock, Windaroo, Queensland, Australia, reports the discovery of a
possible supernova (red mag 14.5, measured by Colin Drescher, Calamvale,
Queensland) on a 30-s unfiltered CCD image taken with a Meade LX200R 35-cm
telescope (+ ST10XE camera) on Oct. 19.408 UT.  The new object is located at
R.A. = 19h54m21s.42, Decl. = -58d42'39".0 (equinox 2000.0; measured by
Drescher), which is 16" west and 10" north of the nucleus of the galaxy IC
4901.  Nothing is visible at this position on an image taken on Sept. 20.52
by Bock (limiting red mag > 17.1) or on a red Digitized Sky Survey image (no
date or limiting magnitude specified).  The variable was designated PSN
J19542142-5842390 when it was posted on the Central Bureau's TOCP webpage and
is here designated SN 2011gv based on the spectroscopic confirmation reported
below.

     N. Morrell, Las Campanas Observatory, Carnegie Supernova Project; and S.
Kafka, Departament of Terrestrial Magnetism, Carnegie Institution of
Washington, report that they obtained a spectrogram (range 300-1100 nm; FWHM
resolution 0.1 nm) of PSN J19542142-5842390 = SN 2011gv on Oct. 20.00 UT with
the 6.5-m Magellan II (Clay) telescope (+ MagE).  The spectrum of 2011gv
consists of a blue continuum with superimposed incipient P-Cyg profiles of
Balmer and He I 587.6-nm lines, consistent with a young type-II supernova.
From emission lines of an underlying H II region, they derive a helicentric
redshift of 0.00682 +/- 0.0002, in good agreement with the recession velocity
measured by Koribalski et al. (2004, A.J. 128, 16) for IC 4901.  Considering
this redshift, the minimum of the H-beta absorption appears blueshifted by
approximately 8900 km/s.  Na I D1 and D2 absorption from the host galaxy is
observed with a total equivalent width of 0.05 nm.  Cross-correlation with a
library of supernvoa spectra using the Supernova Identification tool (SNID;
Blondin and Tonry, 2007, Ap.J. 666, 1024) gives good matches to the spectra
of the type II-P supernovae 1999em and 2005cs at maximum brightness.

     P. Ochner, S. Valenti, S. Benetti, A. Pastorello, and L. Tomasella,
Istituto Nazionale di Astrofisica (INAF), Osservatorio Astronomico di Padova;
and F. Bufano, INAF, Osservatorio Astronomico di Catania, on behalf of a
larger collaboration, report that a spectrum of PSN J19542142-5842390 = 2011gv,
obtained on Oct. 20.05 UT with the New Technology Telescope (+ EFOSC2; range
360-930 nm; resolution 1.8 nm), shows it to be a type-II supernova.  The best
fits to this spectrum found by GELATO (Harutyunyan et al. 2008, A.Ap. 488, 383;
publicly available at https://gelato.tng.iac.es) are with spectra of type-II-
plateau supernovae a few days after explosion.  The blue spectrum is dominated
by a broad H-alpha, mostly in emission, while the other Balmer lines show the
classical P-Cyg profile.  A relatively intense line of He 587.6 nm is also
present.  Adopting a recessional velocity of 2138 km/s for IC 4901 (Koribalski
et al. 2004, A.J. 128, 16; via NED), the expansion velocity deduced from the
H-beta absorption is about 9800 km/s.


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

                         (C) Copyright 2011 CBAT
2011 October 22                  (CBET 2868)              Daniel W. E. Green