[IAUC] CBET 2794: 20110827 : SUPERNOVA 2011fg

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                                                  Electronic Telegram No. 2794
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 2011fg
     W. Zheng and A. Romadan, University of Michigan; J. Vinko, University of
Szeged;  R. Quimby, California Institute of Technology; N. Whallon, B. Sandler,
F. Yuan, and C. Akerlof, University of Michigan; J. C. Wheeler and E.
Chatzopoulos, University of Texas; and G. H. Marion Harvard-Smithsonian Center
for Astrophysics, on behalf of the ROTSE collaboration, report the discovery
of a new supernova (mag about 16.6) in unfiltered images taken on Aug. 20.22
and 25.19 UT with the 0.45-m ROTSE-IIIb telescope at McDonald Observatory.
The new object is located at R.A. = 23h23m20s.59, Decl. = +16o47'41".3
(equinox 2000.0; uncertainty about 1"), which is 1".5 west and 1".1 south of
the center of the host galaxy (SDSS J232320.68+164742.5).  A finding chart
for the object can be found at the following website URL:
http://www.rotse.net/rsvp/j232320.6+164742/ROTSE3_J232320.6+164742.jpg.
     A spectrum, obtained on Aug. 24.24 UT with the 9.2-m Hobby-Eberly
Telescope (+ Marcario Low-Resolution Spectrograph) by S. Rostopchin, shows
that 2011fg is a peculiar type-Ia supernova.  The spectrum contains features
of Si II, S II, and Fe II, characteristics of type-Ia supernovae, but the
strength of the Si II 635.5-nm feature is weaker than normal.  O I 777.5-nm and
the Ca II infrared triplet are also weakly present.  The broad bottom of the
Ca II infrared triplet may be indicative of a shallow high-velocity component.
The SNID code (Blondin and Tonry 2007, Ap.J. 666, 1024) gives mostly normal
type-Ia-supernovae spectra both before and after maximmum as best-fitting
templates, but visual inspection reveals a best match with the spectrum of
SN 2003fg, a peculiar type-Ia supernova at two days after maximum.  The
redshift, estimated from the narrow H_alpha feature from the host, is z =
0.045, which agrees with the photometric z value of the host galaxy in the
SDSS database.  Adopting this redshift estimate, the expansion velocity
from the minimum of the Si II 635.5-nm feature is 9000 km/s, lower than for
normal type-Ia supernovae around maximum light.


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                         (C) Copyright 2011 CBAT
2011 August 27                   (CBET 2794)              Daniel W. E. Green