[vsnet-grb-info 446] GRB 021004: Optical observations at RIKEN

[GCN Circulars <gcncirc@lheawww.gsfc.nasa.gov>]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  1589
SUBJECT: GRB 021004: Optical observations at RIKEN
DATE:    02/10/06 09:09:05 GMT
FROM:    Ken ichi Torii at RIKEN  <torii@crab.riken.go.jp>

K. Torii (RIKEN), T. Kato (Kyoto Univ.), and H. Yamaoka (Kyushu Univ.)
report:

 In response to the GCN/HETE burst position notice, a part of the
error region of GRB 021004 (Shirasaki, et al., GCN 1565) was observed
by the automated system at RIKEN. Starting at 12:09:27 UT (193-s after
the burst trigger), 30-s exposures were repeated with the 0.20-m
reflector equipped with unfiltered CCD AP7p.

 Frequent passages of clouds significantly degraded the limiting
magnitudes of the data. The optical afterglow reported by Fox (GCN
1564) is not visible in our early phase images. Comparison with the
USNO-A2.0 red magnitudes gave the following 3-sigma upper limits for
the afterglow. Further analyses for the full data set are in progress.

----------------------------------------
Mean epoch     From GRB   Magnitude  
----------------------------------------
12:09:42 UT    208 s      > 13.6    
12:10:21       247        > 13.6    
12:11:00       286        > 13.6    
12:11:40       326        > 14.2
12:12:19       365        > 13.6
----------------------------------------

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