TITLE:   GCN CIRCULAR
NUMBER:  9811
SUBJECT: GRB 090813: CrAO optical obsevations
DATE:    09/08/15 09:29:00 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

A. Volnova (SAI MSU), E. Pavlenko, O. Antoniuk, V. Rumyantsev (CrAO), A. 
Pozanenko (IKI)  report on behalf of larger GRB follow-up collaboration:

We observed the field of the Swift GRB 090813 (Cummings et al. GCN 9781) 
starting (UT) Aug. 13 23:57:26 with Shajn telescope of  CrAO under favorable 
weather condition and seeing ~1.6".
At the place of optical afterglow (Gorosabel et al. GCN 9782; Cenko et al. 
GCN 9783; Smith et al. GCN 9784) we detect a source which appears slightly 
E-W extended.

Preliminary photometry of the source in a combined image based on  USNO-B1.0 
star (RA(J2000)=15:02:47.99, Dec(J2000)=88:31:41.4) assuming R= 14.23 is 
following:

T0+     Filter, Exposure, mag.,     err.
(d)             (s)

0.8440   R       57x60     20.50 +/-0.06

Observations will be continued.