TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  1378
SUBJECT: GRB 020124: Optical observations
DATE:    02/04/19 12:32:47 GMT
FROM:    Ken ichi Torii at RIKEN  <torii@crab.riken.go.jp>

K. Torii (RIKEN), T. Kato (Kyoto U.), H. Yamaoka (Kyushu U.), and
A. Yoshida (Aoyama Gakuin U., RIKEN) report:

 Based on the GCN alert notice, the GRB 020124 (Ricker, et al. GCN
1220) was observed at RIKEN with the 0.25m f/3.4 hyperboloid
astro-camera equipped with unfiltered cooled CCD AP7p. The field of
view was 50'x50' which covered the HETE's entire error region of 12'
radius (GCN 1220).  The observation started at 2002/1/24 12:43 UT (122
minutes after the burst) and 126 frames of 20-s exposure were acquired
by 13:47 UT. The central time of all the exposures were 2002/1/24
13:15 UT. 

 PSF photometry was applied to each frame and then stacked to yield
3.0-sigma detection of the optical afterglow at the position reported
by Price et al. (GCN 1221). By using 21 nearby comparison stars from
the Henden's field photometry (GCN 1251), we derive the afterglow's
magnitude as R=18.5 mag. The 1-sigma error range is estimated to be
between R=18.2 and R=18.9.

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