[IAUC] CBET 3587: 20130716 : SUPERNOVA 2013dx = GRB 130702A

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                                                  Electronic Telegram No. 3587
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)
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SUPERNOVA 2013dx = GRB 130702A
     S. Schulze, Pontificia Universidad Catolica de Chile and Millennium
Center for Supernova Science; G. Leloudas, Oskar Klein Centre, Stockholm
University, and Dark Cosmology Centre, Niels Bohr Institute; D. Xu, Dark
Cosmology Centre, Niels Bohr Institute; J. P. U. Fynbo, Dark Cosmology Centre,
Niels Bohr Institute; S. Geier, Nordic Optical Telescope Observatory and Dark
Cosmology Centre, Niels Bohr Institute; and P. Jakobsson, University of
Iceland, on behalf of a larger collaboration, report that they have been
monitoring the optical counterpart of GRB 130702A [discovered with the Fermi
spacecraft and localized by the iPTF survey; cf. Cheung et al., GCN Circular
14971, posted at website URL http://gcn.gsfc.nasa.gov/gcn3/14971.gcn3;
Collazzi et al., GCN Circ. 14972; and Singer et al., GCN Circ. 14967 (R.A. =
14h29m14s.78, Decl. = +15d46'26".4, equinox 2000.0; R-band mag 17.4 on July
2.178 UT, 4.2 hr after the gamma-ray-burst trigger, from imaging with the
Palomar 1.2-m Oschin Schmidt telescope, but 3.8 deg from the gamma-ray
position; nothing detected at this position on an Oschin image from 2011 Feb.
5, limiting R mag > 21.1)].  The authors obtained spectroscopy of the optical
counterpart with the 2.5-m Nordic Optical Telescope (NOT) at Roque de los
Muchachos Observatory in La Palma, Spain, 5.97 days after the onset of the
gamma-ray burst; this is 5.21 days in the burst rest frame (z = 0.145; cf.
Mulchaey et al., posted at http://www.astronomerstelegram.org/?read=5191;
Leloudas et al., GCN Circ. 14983).  Observations consisted of three 1200-s
exposures with grism #4, covering the range 375-900 nm with a resolution of
about 300.  The flux-calibrated spectrum presents clear deviations from a
single decaying power law, which is expected for a GRB optical afterglow
alone.  In particular, two broad emission features are clearly evident,
peaking at about 490 and 560 nm with a local minimum at about 520 nm (all in
the observer frame).  Via the SNID software (Blondin and Tonry 2007, Ap.J.
666, 1024) and SUPERFIT (Howell et al 2002, Bull. AAS 34, 1256), the spectrum
resembles the broad-lined type-Ic supernova 1998bw at 7-8 days after its
explosion (Patat et al. 2001, Ap.J. 555, 900).

     V. D'Elia, Agenzia Spaziale Italiana Science Data Center, and Osservatorio
Astronomico di Roma (OAR), Istituto Nazionale di Astrofisica (INAF); P.
D'Avanzo and A. Melandri, Osservatorio Astronomico di Brera (OAB), INAF; M.
Della Valle, Osservatorio Astronomico di Capodimonte, INAF; G. Tagliaferri,
OAB, INAF; D. Malesani, Dark Cosmology Centre, Niels Bohr Institute,
University of Copenhagen; E. Pian, Scuola Normale Superiore, Pisa; L. A.
Antonelli and S. Piranomonte, OAR, INAF; and A. Harutyunyan and D. Carosati,
INAF and Galileo National Telescope (TNG), on behalf of the CIBO
collaboration, report on continued monitoring of the optical counterpart of
the Fermi-spacecraft gamma-ray burst designated GRB 130702A (GCN Circ. 14967)
with the Italian 3.6-m TNG telescope located in the Canary Islands, equipped
with the DOLoRes camera, on the nights of July 5 and 9 (four and eight days
after the Fermi GBM trigger).  The optical counterpart was detected at 7.92
days after the GRB outburst (which itself was detected on July 2.00374 UT)
in the SDSS r band with a magnitude of 19.91 (calibrated against nearby SDSS
stars).  Also starting at July 9.92, they obtained a 2000-s spectrogram
(wavelength range 390-820 nm; resolution R about 600) with the LR-B grism,
the spectrum being considerably redder than on July 5 and showing a continuum
similar to that of SN 1998bw (Patat et al. 2001, Ap.J. 555, 900) and other
GRB-associated supernovae.  In particular, they detect a strong emission at
about 430.0 nm that bears similarity with SN 2006aj (Pian et al. 2006, Nature
442, 1011) and 1997ef (Iwamoto et al. 2000, Ap.J. 534, 660) spectra obtained
close to maximum light.


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                         (C) Copyright 2013 CBAT
2013 July 16                     (CBET 3587)              Daniel W. E. Green