[IAUC] CBET 3200: 20120810 : SUPERNOVA 2012eb = GRB 120714B

[quai en eps.harvard.edu]

                                                  Electronic Telegram No. 3200
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 2012eb = GRB 120714B
     A gamma-ray burst designated GRB 120714B was announced on GCN Circular
13471 (posted at website URL http://gcn.gsfc.nasa.gov/gcn3/13471.gcn3)
by C. J. Saxton et al.; it was detected on July 14.888 UT by the Swift
Burst Alert Telescope (BAT); the Swift/XRT position for the source was given
on GCN Circular 13473 as R.A. = 23h41m38s.35, Decl. = -46d11'07" (equinox
2000.0), with the UVOT white-filter magnitude given as 18.6 with position
end figures 38s.05, 03".  By July 15.126, the afterglow of GRB 120714B had
faded to magnitude g' about 22.3 (GCN Circular 13478).

     Sylvio Klose, Thueringer Landessternwarte (TLS), Tautenburg; J. Greiner,
Max Planck Institute for extraterrestrial Physics, Garching, (MPE); J. Fynbo,
DARK Cosmology Centre, Niels Bohr Institute, University of Copenhagen; A.
Nicuesa Guelbenzu and S. Schmidl, TLS; A. Rau, MPE; and T. Kruehler, DARK
Cosmology Centre, on behalf of a larger collaboration, report that the
Gamma Ray Burst Oprical Near Infrared Detector (GROND; a 7-channel imager
mounted at the 2.2-m ESO/MPG telescope at La Silla; cf. Greiner et al. 2008,
PASP 120, 405) has been following the afterglow of GRB 120714B (Saxton et al.,
GCN Circ. 13471) at z = 0.398 (Fynbo et al., GCN Circ. 13477) since July 15
(Nicuesa Guelbenzu et al., GCN Circ. 13478).  The light of the optical
transient has been fading in all GROND optical bands during the first 1.5
days, was then flattening in r', i', and z' bands, and finally rising at
about three days after the trigger (while it is flattening in g').  The data
suggested that this behavior can be interpreted as an upcoming supernova
component with a an early rise similar to the supernova associated with GRB
011121 at z = 0.36 (Bloom et al. 2002, Ap.J. 672, 45; Garnavich et al. 2003,
Ap.J. 582, 924; Greiner et al. 2003, Ap.J. 599, 1223; Price et al. 2002,
Ap.J. 572, 51).
     Spectroscopy of the optical transient with the Very Large Telescope (+
FORS2) was performed on Aug. 1/2, or 18.3 days after the burst.  Observations
were done with the 300V grism, covering the wavelength range from 445 to 865
nm, and lasted 7200 s.  The spectrum reveals very broad features in the
continuum, with a prominent peak around 650.0 nm and broad lines of Si II
and Ca II, in agreement with a broad-lined supernova dominating the light of
the optical transient.  At present, a decision between type Ib and Ic events
cannot be performed due to an uncomfortable presence of atmospheric features
in the spectrum.


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

                         (C) Copyright 2012 CBAT
2012 August 10                   (CBET 3200)              Daniel W. E. Green