TITLE:   GCN CIRCULAR
NUMBER:  11078
SUBJECT: GRB100807A: optical observation in CrAO
DATE:    10/08/09 15:05:23 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

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

We observed the field of the Swift GRB 100807A (Grupe  et al., GCN 11067) 
with Shajn telescope of CrAO in filter R between (UT) Aug. 07 22:58:14 --  
Aug. 08 01:17:44 under descending seeing with mean value of ~ 2.1". We do 
not detect the afterglow (Cenko, GCN 11073). The extended object ~ 8" was 
detected in coordinates (J2000) center RA:  03 41 12.92 Dec: +67 40 19.4. 
The position of optical afterglow  (Cenko, GCN 11073) is in the edge of the 
extended object.

The photometry is based on USNO-B1.0 star 1576-0084708  (J2000) RA= 03 41 
11.50  Dec= +67 39 58.1  (assuming  R=16.37):

T0+      Filter,   Exposure, Ext. Object mag.           Upper Limit
(mid, d)              (s)

0.6214  R       97x60       23.0 +/- 0.2                    23.8

With upper limit of R=23.8 we confirm the fading nature of afterglow of  GRB 
100807A (Grupe  et al., GCN 11067). The extended object might be a host 
galaxy of GRB 100807A.

The combined images can be found 
http://grb.rssi.ru/GRB100807A/GRB100807a_100807_R_ZTSh.gif