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GCN Circular 1298

GRB 020322 optical observation
2002-03-23T11:13:57Z (22 years ago)
Jochen Greiner at Astrophys.Inst. Potsdam,Germany <>
J. Greiner (MPE Garching, AIP Potsdam), 
U. Thiele (MPIA Heidelberg, Calar Alto), 
S. Klose (Thueringer Landessternwarte Tautenburg), 
A.J. Castro-Tirado (LAEFF-INTA, Madrid, and IAA-CSIC, Granada) report:

We have imaged the location of GRB 020322 with the 3.5 m telescope
at Calar Alto (Spain) for three times 10 min. between 22 Mar 2002 23:46 UT
to 23 Mar 2002 00:09 UT at a seeing of 1.4 arcsec. Based on the same USNO
star at 18:00:58.03, +81:06:08.3 listed as having R=17.5 mag we measure
the following magnitudes for the three sources a, b, c (Bloom et al.; GCN 1296)
inside the XMM error circle (Ehle et al.; GCN 1293):

         Calar Alto            earlier measurement
  a   22.07 +- 0.06 mag      21.9 mag (Szentgyorgyi et al; GCN 1295)
  b   23.80 +- 0.30 mag      23.26 +- 0.32 mag (Bloom et al.; GCN 1294)
  c   24.50 +- 0.60 mag 

While object c is at our detection threshold, object b has clearly faded,
as also a visual comparison with the FITS image of Bloom et al. (GCN 1296) 
shows (though the errors formally allow for constancy of source b). 
We therefore suggest that source b is the optical counterpart of GRB 020322.
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