[vsnet-grb-info 14256] GRB 131127A: optically dark burst

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  15570
SUBJECT: GRB 131127A: optically dark burst
DATE:    13/12/03 16:26:09 GMT
FROM:    Alina Volnova at SAI MSU  <alinusss at gmail.com>

A.Volnova (IKI), E. Klunko (ISTP), M. Eselevich (ISTP), A.
Pozanenko(IKI) report on behalf of larger GRB follow-up collaboration:

We report about revised photometry of the GRB 131127A (Markwardt et
al., GCN 15516) published earlier (Klunko et al., GCN 15519).
Using combined image of full data set of the observations on Nov. 27
we do not detect any optical counterpart in the enhanced XRT error
circle (Evans et al., GCN 15520). The details of the photometry are
the following:

UT start       t-T0           Filter    Exp.   OT   UL
                 (mid, days)             (s)             (3 sigma)
10:40:06     0.04680      R         4650   n/d   22.5

The photometry is based on the same 3 USNO-B1.0 stars listed in the GCN 15519.

The deep upper limit obtained at ~67 min (mid time) after burst
trigger together with Swift/XRT observations
(www.swift.ac.uk/xrt_curves/00579571/flux.qdp) suggests the upper
limit of optical-to-X-ray spectral slope beta_OX = -0.02 and classify
the GRB 131127A as a dark burst according to Jakobsson (Jakobsson et
al., 2004, ApJ, 614, L21).