TITLE:   GCN CIRCULAR
NUMBER:  7890
SUBJECT: GRB 080603b: optical observation
DATE:    08/06/21 11:40:18 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

E. Klunko (ISTP), A. Pozanenko (IKI) on behalf of larger GRB follow up 
collaboration  report:

We observed afterglow (Rujopakarn, et al., GCN 7792) of Swift GRB 0800603b 
(Mangano et al., GCN 7794)  with 1.5 m telescope of Sayan observatory 
(Mondy) on Jun.04 between (UT) 18:35 - 19:11. The afterglow is detected in a 
combined image of 8x120 s exposure. A photometry of the afterglow obtained 
against several USNO-A2.0 stars is following:

T0+       Exposure  R_mag
(mid)

0.9686 d  8x120 s   21.10 +/- 0.10

This photometry confirms the steep decay of a light curve (alpha ~ 2.5) 
suggested by Kann et al. (GCN 7824).
The message may be cited.