Electronic Telegram No. 3677
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 2013fu = GRB 130831A
     Sylvio Klose and A. Nicuesa Guelbenzu, Thueringer Landessternwarte,
Tautenburg; T. Kruehler, European Southern Observatory (ESO); J. Greiner, D.
A. Kann, and A. Rau, Max Planck Institute for Extraterrestrial Physics,
Garching; F. Olivares E., Universidad Andres Bello, Chile; and S. Schulze,
Pontificia Universidad Catolica, Santiago, on behalf of a larger collaboration,
report that they observed the optical transient after the reported outburst of
the gamma-ray burst GRB 130831A (first detected on Aug. 31.54462 UT by Hagen et
al., and reported on GCN Circ. 15139, as posted at the following website URL:
http://gcn.gsfc.nasa.gov/gcn3/15139.gcn3; R.A. = 23h54m36s, Decl. = +29d26'53",
equinox 2000.0, uncertainty 3') with the Very Large Telescope (+ FORS2,
equipped with the 300V grism) on Sept. 29 and 30, between 28.5 and 29.5 days
after the burst under excellent sky conditions with mean seeing around 0".6.
The total exposure time of the spectrogram (wavelength range approximately
440-920 nm) was 1.53 hr.  In the combined spectrum, the optical emission was
detected over the full spectral range.  The spectrum peaks at about 800 nm and
shows broad absorption features, very much reminiscent of the spectrum of, e.g.,
SN 2003lw = GRB 031203 (z = 0.1055; IAUC 3808; Malesani et al. 2004, Ap.J. 609,
L5) and the more recent objects SN 2012eb = GRB 120714B (z = 0.40; Klose et al.
2012, GCN 13613), SN 2013ez = GRB 130215A (z = 0.597; CBET 3637; de Ugarte
Postigo et al., GCN 14303), SN 2013cq = GRB 130427A (z = 0.34; CBET 3531; Xu et
al. 2013, Ap.J. 776, 98), and SN 2013dx = GRB 130702 (z = 0.145; CBET 3587;
Schulze et al. 2013, GCN 14994) -- all obtained around maximum light of the
supernovae.  The conclusion is that this shows the spectroscopic discovery of
the appearence of a broad-line supernova following GRB 130831A at z = 0.4791
(Cucchiara et al. 2013, GCN 15144), confirming the suggestion of Pozanenko et
al. (GCN 15237) based on the optical light curve.  It is uncertain as to
whether SN 2013fu is a type-Ib or type-Ic supernova.
     Guidorzi et al. (GCN 15140) reported detection of the fading optical
counterpart of GRB 130831A at magnitude R = 14.1 on Aug. 31.54793 UT.  Yoshii
et al. (GCN 15143) measured magnitudes g' = 15.4 and R_c = 15.2 on Aug.
31.5470.  Xu et al. (GCN 15142) found r' = 14.4 on Aug. 31.8802 and r' = 15.7
on Sept. 1.2021.


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

                         (C) Copyright 2013 CBAT
2013 October 25                  (CBET 3677)              Daniel W. E. Green