[IAUC] CBET 2824: 20110925 : SUPERNOVA 2011fr

[quai en eps.harvard.edu]

                                                  Electronic Telegram No. 2824
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 2011fr
     W. Zheng, University of Michigan; J. Vinko, University of Szeged; R.
Quimby, IPMU University of Tokyo; N. Whallon, A. Romadan, B. Sandler, and C.
Akerlof, University of Michigan; F. Yuan, Australian National University; 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 transient (mag about 18.8) in
unfiltered images taken on Sept. 1.30 UT with the 0.45-m ROTSE-IIIb telescope
at McDonald Observatory.  The new object, which was observed again on Sept.
7.23 at mag about 18.2 and on Sept. 21.22 at mag about 17.8, is located at
R.A. = 1h29m45s.8, Decl. = +18o53'07".2 (equinox 2000.0; uncertainty about 1"),
which is 1".1 west and 8".8 north of the center of the host galaxy SDSS
J012945.87+185258.3; a finding chart for the object can be found at website
URL http://www.rotse.net/rsvp/j012945.8+185307/ROTSE3_J012945.8+185307.jpg.
     A spectrum, obtained on Sept. 22.23 UT with the 9.2-m Hobby-Eberly
Telescope (+ Marcario Low-Resolution Spectrograph) by J. Caldwell, shows
that 2011fr is most probably a type-IIn supernova.  The spectrum consists of
emission features of H and He I, superimposed on a blue continuum.  An
active-galactic-nucleus outburst can be ruled out since the source is clearly
off-centered within the galaxy on the HET finder images.  The H emission
profiles are of Lorentzian shape, having FWHMs of 1200, 1500, and 2000 km/s
for H-alpha, H-beta, and H-gamma, respectively.  No P-Cygni component can be
detected for any of the observed emission features.  The redshift estimated
from the emission peaks is z = 0.0596, which is consistent with the photo-z
of the presumed host galaxy in the SDSS database.  Adopting this redshift,
the brightness measured by ROTSE corresponds to absolute magnitude -19.1,
which is brighter than most core-collapse supernovae, being close to the
peak brightness of type-Ia supernovae.  This suggests that interaction
between ejecta and circumstellar material may contribute significantly to the
observed luminosity.  Although the appearance of the spectrum is similar to
that of the super-luminous supernova 2008am (Chatzopoulos et al. 2011, Ap.J.
729, 143), the observed brightness is below the fiducial lower limit (mag -20)
of such extreme events.


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                         (C) Copyright 2011 CBAT
2011 September 25                (CBET 2824)              Daniel W. E. Green