TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  1716
SUBJECT: GRB021004 Chandra Observation
DATE:    02/12/01 06:19:13 GMT
FROM:    Fiona Harrison at CalTech  <fiona@srl.caltech.edu>

M. Sako & F. A. Harrison report on behalf of the Caltech-NRAO 
collaboration:

We report a second TOO observation of GRB021004 taken with the Advanced CCD
Imaging Spectrometer (ACIS-S) onboard the Chandra X-ray Observatory.  The
observation started at 17:35 on November 25 (52.229 days after the GRB) for a
total exposure time of 30.0 ksec.  Ten counts were detected in a circular
region with a radius of 1 arcsec centered on the source position of GRB021004,
of which 1 - 2 photons are estimated to be background events.  Assuming the
same power-law spectral index as that observed during an earlier Chandra observation
(GCN 1624), this corresponds to a 2 - 10 keV flux of (7.2 +/- 2.5) x 10^-16
erg/cm2/s.  The source, therefore, has decayed with a characteristic power
law decay time slope of approximately -1.7 since the previous observation.

The data can be accessed through the Chandra Data Archive.  We thank Harvey
Tananbaum for allocating Director's Discretionary Time and the Chandra X-ray
Center for implementing the obervation.