[vsnet-grb-info 11074] GRB 111022B: BTA Optical Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  12491
SUBJECT: GRB 111022B: BTA Optical Observations
DATE:    11/10/24 19:37:43 GMT
FROM:    Vladimir Sokolov at SAO RAS  <sokolov at sao.ru>

A. S. Moskvitin, V. N. Komarova, V. V. Sokolov and T. N. Sokolova
(SAO RAS GRB follow-up team) report:

The field of GRB 111022B (Holland et al., GCN#12472) was observed
with the 6-m BTA/Scorpio on October, 23, 2011. We obtained 3 x 180 sec.
frames in the Rc band and 25 x 120 sec. in the Ic band.
Observations in Rc began at 00:40:10 (7.5 hours after the trigger),
ended at 00:50:21 UT; in Ic began at 01:23:11 UT (8.2 hours after the
trigger), ended at 02:22:40 UT. Conditions were clear with a seeing
of about 1".2 (FWHM of stellar objects in the Ic co-added image).

The possible optical counterpart is clearly detected in the Ic band
within the 1".5 XRT error circle (according to
http://www.swift.ac.uk/xrt_positions/) at the coordinates:
R.A.  (J2000) = 07:15:51.56
Decl. (J2000) = +49:41:01.7
with the uncertainty 0".2.

The object magnitude is I = 23.6 +/- 0.3 as compared to USNO-B1.0 Imag
of six nearby stars. The high error is due to calibration, the 3-sigma
limit of the Ic co-added image is about 24.7. We do not detect the object
in the Rc-band down to the 3-sigma level limiting magnitude of about 24.3.
The Ic image can be found at
ftp://ftp.sao.ru/pub/grb/GRB111022B/GRB111022B_BTA.jpg

Our results are in agreement with the previously reported NOT observations
(Vreeswijk et al., GCN#12479) and do not contradict the idea of a high
redshift burst according to Gemini infrared observations (Levan et al.,
GCN#12481).

We are grateful to T. A. Fatkhullin
and the BTA staff for the help in observations.