[vsnet-grb-info 2255] GRB051006: optical observations

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  4094
SUBJECT: GRB051006: optical observations
DATE:    05/10/14 15:15:37 GMT
FROM:    Vasilij Rumjantsev at CrAO  <rum at crao.crimea.ua>

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

We have observed the GRB051006 error box (Norris et al., GCN4061) with 2.6 m
Shajn telescope of CrAO on October 7 and 8 in R-band.  On Oct.8 within XRT
error circle (Capalbiet al., GCN4066) we detect source #3 quoted by Ugarte
et al. (GCN 4064). The coordinate of the source is

RA(J2000) = 07 23 13.52
Dec          = +09 30 24.48

with uncertainty 0.4 arcsec in both coordinates. The photometry of the
source against of USNO A2.0 is following

Mid time     Exposure    R
Oct.8 (UT)
  02:28      35x120 s   22.20 +/-0.15

The stacked image of the Oct.8 observation can be found in
http://grb.rssi.ru/GRB051006/grb051006_051008_ZTSh_R.gif

Taking into account the upper limit  of R>21.0 at 12.9 hours after the burst
(Bradley Cenko at al., GCN 4068) and our result  above one can estimate the
power law decay index of possible afterglow source #3 as alpha >-1.37.

In our observation on Oct.7 between 02:23 - 02:44 (UT) due to unfavorable
weather conditions the seeing was ~5 arcsec. At this time we could not
confirm the presence of source #3 in the tail of nearby bright star.
Detailed analysis in underway.

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