TITLE:   GCN CIRCULAR
NUMBER:  7887
SUBJECT: GRB 0800603A: optical observation
DATE:    08/06/18 00:38:23 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 (Gomboc et al., GCN 7788; Chornock  et al., GCN 7789)
of GRB 0800603A  (Paizis et al., GCN 7790)  with 1.5 m telescope of Sayan
observatory (Mondy) on Jun.03 between (UT) 18:21:30 - 18:43:55. The
afterglow is detected in each frame of 120 s exposure.
Coordinates  of the afterglow obtained from a combined image are R.A.(J2000)
= 18 37 38.04  Dec.(J2000) = +62 44 39.4 with uncertainties of 0.3". A
photometry of the afterglow obtained against several USNO-A2.0 stars is
following:

T0+       Exposure  R_mag
(mid)

0.3015 d  8x120 s   20.49 +/- 0.03

The photometry might be slightly contaminated by the nearby source(s)
(Perley
et al., GCN 7870, Rumyantsev et al., GCN 7860).

In comparison to the magnitude measured in early epoch (Perley et al. GCN
7791) the index of power law decay is ~ 0.5 which is compatible with slow
decay index (alpha ~ 0.5) obtained by Kann et al. (GCN 7822).

The combined image can be found at
http://grb.rssi.ru/GRB080603A/GRB080603A_R_AZT33.jpg

The message may be cited.