TITLE:   GCN CIRCULAR
NUMBER:  11154
SUBJECT: GRB 100823A: optical upper limit
DATE:    10/08/27 20:45:22 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

K. Antoniuk, V. Rumyantsev (CrAO), A. Pozanenko (IKI) report on behalf of 
larger GRB  follow-up collaboration:

We observed the field of the Swift GRB 100823A (Mangano et al. GCN 11135) 
with AZT-11 telescope of CrAO observatory. Several images in R-filter were 
obtained on Aug. 23 between (UT) 22:05 - 22:53.

In enhanced XRT position (Goad et al. GCN 11136) we do not detect any source 
up to R=20.7. The photometry of stacked image is based on  USNO-B1.0 star 
0958-0013520 located at RA(J2000) = 01:22:45.50, DEC(J2000) = +05:49:03.0 
(assuming R=16.75):

 t-T0,       Filter,   Exposure,    OT,       Upper limit (3 sigma)
(mid, d)               (s)
 0.2111   R         15*180         n/d           20.7