TITLE:   GCN CIRCULAR
NUMBER:  15484
SUBJECT: GRB 131108A: optical observations
DATE:    13/11/14 06:19:25 GMT
FROM:    Alina Volnova at SAI MSU  <alinusss@gmail.com>

A. Volnova (IKI), Yu. Krugly (IA KhNU), R. Inasaridze (AAO), I.
Slyusarev (IA KhNU),  G. Inasaridze (AAO), V. Zhuzhunadze (AAO),  I.
Molotov (KIAM), A. Pozanenko (IKI) report on behalf of larger GRB
follow-up collaboration:

We observed the field of Swift GRB 131108A (Racusin et al., GCN 15464,
Hurley et al. GCN 15466) with  AZT-8  telescope of Institute of
Astronomy, Kharkiv National University and with AS-32 telescope of
Abastumani Observatory. We obtained several images in R-filter and
also non-fileterd images.   Within the enhanced XRT circle (Stroth &
Kennea, GCN 15474) we detect the optical counterpart reported by
Gorosabel et al. (GCN 15469).

The details of preliminary photometry are following:

UT start                     t-T0    Filter  Exp.   OT
                              (mid, days)       (s)

2013-11-10T02:00:12 1.24560 R       15x300  20.92 +/- 0.12
2013-11-11T00:44:00 2.21609 None    36x120  21.20 +/- 0.11

The photometry is based the SDSS stars, R magnitude (gri -> R
transformations by Lupton 2005):

SDSS id                           R
J102559.54+093904.1   16.928 +/- 0.014
J102609.18+093958.8   17.999 +/- 0.021
J102610.10+093859.6   17.339 +/- 0.014