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GCN Circular 1576

GRB 021004, optical observations
2002-10-05T10:40:35Z (22 years ago)
Peter Garnavich at U of Notre Dame <>
J. Winn, D. Bersier, K.Z. Stanek (Harvard-Smithsonian Center
for Astrophysics), P. Garnavich (Notre Dame) and A. Walker (CTIO)

Images of the afterglow associated with GRB 021004 (GCN 1564)
were obtained with the CTIO 4m + Mosaic Camera and
the Fred Whipple Observatory 1.2m telescope beginning
at Oct. 5.15 (UT). Preliminary analysis of the
R-band images provide the following magnitudes
assuming the USNO star noted in GCN 1573 has a
magnitude of R=15.64:

Oct. 5 UT   R
  03:00    19.10
  04:46    19.21
  05:55    19.24
  07:23    19.25
  08:43    19.23
  09:53    19.31

These data indicate that the rapid decay (GCN 1573)
has slowed considerably. The power-law index of
the optical light between 15 and 22 hours after the
burst is only 0.37. This behavior is similar
to the bump seen in GRB 000103c which may have been
due to a microlensing event (Garnavich, Loeb & Stanek
2000, ApJ, 554, 11). Monitoring this object at a
moderate time resolution is urged.

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