[vsnet-grb-info 1861] GRB050713b: Maidanak optical observations

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  3701
SUBJECT: GRB050713b: Maidanak optical observations
DATE:    05/07/29 21:05:39 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen at iki.rssi.ru>

D. Sharapov,  M. Ibrahimov (MAO), V.Rumyantsev (CrAO), A.Pozanenko (IKI) on
behalf of larger GRB follow up collaboration report:


We observed the error box of GRB050713b (Trigger #145754; Vaughn et al., GCN
3590,   Parsons et al., GCN 3600) with 1.5m telescope (Maidanak Astronomical
Observatory) on July 13, 14, and 15. Limiting magnitude of stacked image of
observation obtained on July 13 (start time July 13 UT 18:06, i.e. ~6.0 h
after burst) is R=23.2.   We detected optical sources S1 which is offset
~1.9
arcsec of the refined XRT error circle (Page et al., GCN3602) and have the
following coordinates (uncertainty in each coordinate is about 1 arcsec):

S1 RA(J2000)= 20 31 15.96   Dec(J2000) = +60 56 36.4

Photometry of the source based on USNO A2.0 catalog is following:

Mean time         Exposure   S1
  (UT)               sec.    mag.

July 13, 18:56    15x300     24.13 +/-0.74
July 14, 19:44     8x300     22.90 +/-0.44
July 15, 19:31     9x300     22.93 +/-0.30


Since the S1 source does not demonstrate fading behavior, it is unlikely
that S1
is an OT of GRB050713b.

Stacked image of July 13 observations can be found in
http://grb.rssi.ru/GRB050713b.

This message may be cited.