GCN Circular 1606

E.A.Barsukova (SAO), V.P.Goranskij (Sternberg Institute),
G.M.Beskin (SAO), V.L.Plokhotnichenko (SAO), A.S.Pozanenko  (IKI).

We have observed the GRB021004 afterglow (GCN 1564
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 ) with SAO RAN
1-m Zeiss telescope and UBVRcIc photometer with Electron K-585
CCD.  Observations cover time interval from 7 to 12 hours after
the burst. Exposure time of each frame is 10 minutes, the field
is 3'x4'. Results of the photometry are in the table below. Standards
are taken relative to A.Henden and U.Munari, AsApSuppl. v.143,
343 (1999) standard near V407 Cyg.

        R.A., Decl, 2000          Rc        V        B
       position from A1.0
    C 0 26 57.9 +18 56 07   16.35    16.71    17.15
    F 0 26 58.7 +18 56 56   15.53    16.30    17.13
 +/-0.01  +/-0.02  +/-0.02
    a 0 26 52.0 +18 55 13   13.85    14.55    15.29
 +/-0.01  +/-0.02  +/-0.02

  Date             UT           mag
               (Mean epoch)

  filter=Rc, Typical errors=0.05

  021004   18  58  12    17.89
  021004   19  31  49    17.88
  021004   20  05  28    18.06
  021004   20  41  33    18.09
  021004   21  25  37    18.17
  021004   21  58  50    18.35
  021004   23  08  06    18.39
  021004   23  41  19    18.54
  021005   00  03  05    18.57

  filter=V, Typical errors=0.07

  021004   19  09  24    18.33
  021004   19  42  55    18.34
  021004   20  19  36    18.43
  021004   20  52  43    18.45
  021004   21  02  35    18.60
  021004   21  36  45    18.66
  021004   22  09  46    18.82
  021004   23  27  40    18.89
  021004   23  52  09    18.87

  filter=B, Typical errors=0.10

  021004   19  20  49    18.67
  021004   19  54  03    18.78
  021004   20  30  35    18.77
  021004   21  14  29    18.98
  021004   21  47  49    19.10
  021004   22  20  46    19.05
  021004   23  30  11    19.26

The data obtained is compatible with achromatic decay.
Analysis of the data set is underway and result will be improved.
The figures of BVRc observations may be found in
http://grb.rssi.ru/GRB021004/

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