[vsnet-grb-info 14098] GRB 131030A: SAO RAS optical observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  15412
SUBJECT: GRB 131030A: SAO RAS optical observations
DATE:    13/10/31 10:36:52 GMT
FROM:    Vladimir Sokolov at SAO RAS  <sokolov at sao.ru>

A. S. Moskvitin,
reports on behalf of SAO RAS GRB follow-up team:

We observed the field of GRB 131030A (Troja et al., GCN#15402)
with the 1-meter telescope Zeiss-1000 of Special Astrophysical
Observatory of RAS in four bands: B, V, Rc, Ic. Observations
were started since 23 minutes after the Swift trigger.
The weather conditions were excellent, but the air masses of
the object was about 3-6.

Optical counterpart was clearly detected at all images.
Preliminary results of Rc band photometry are as following:

T_mid, UT   T - T0, h   exposure, s   R mag   +/- error
21:18:45    0.374        60           16.55 +/- 0.02
21:34:05    0.630        60           17.09 +/- 0.03
21:44:14    0.799       120           17.26 +/- 0.02
21:56:27    1.003       120           17.39 +/- 0.03
22:07:26    1.186       120           17.53 +/- 0.03
22:21:30    1.420       360           17.63 +/- 0.02
22:30:08    1.564       480           17.69 +/- 0.03

The magnitudes were calibrated against the set of USNO B1 stars
(R2) and not corrected for the Galaxy extinction.
Rc band light curve and the first image is shown at
ftp://ftp.sao.ru/pub/grb/GRB131030A/GRB131030A_image_LC.jpg