GCN Circular 7887
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.