TITLE:   GCN CIRCULAR
NUMBER:  7883
SUBJECT: GRB 080603A: optical observations on June 04
DATE:    08/06/14 11:28:28 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  a field of  INTEGRAL GRB 080603A (Paizis et al., GCN 7790) in 
R-band on June 04 between (UT) Jun.04 23:18:41 - Jun.05 00:12:41 with 
Zeiss-1000 (Simeiz) telescope of CrAO observatory.   At  the place of the 
optical afterglow (Gomboc et al., GCN 7788; Chornock  et al., GCN 7789) we 
detect an object with coordinates

RA(J2000):  18 37 38.02
Dec(J2000): +62 44 39.44

Within uncertainties (0.5" or better ) the coordinates of the object are 
consistent with reported early (Gomboc et al., GCN 7788; Chornock  et al., 
GCN 7789) and one can consider the object as afterglow of GRB 080603A.

A group of two extended sources (Perley et al., GCN 7870)  is not resolved 
in our later observation on 3.496 d (Rumyantsev et al. GCN 7860). The 
unresolved  source (Rumyantsev et al. GCN 7860)  lies ~1.8" south from the 
afterglow position. And tentatively one can consider the upper limit of the 
observation on 3.496 days  R=22.85 (3sigma) as an upper limit of the 
afterglow brightness.

Based on  USNOB1.0 star with ID 1527-0313986 at RA = 18:37:55.186, Dec. 
+62:45:32.28 (R1 = 16.74)  we estimated brightness of  the afterglow on 
1.521 days:

UT,       Exposure,   R_mag, UL
(mid time)

1.521 d  27x120 s  22.2 +/- 0.2   22.9

This message may be cited.