TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  220
SUBJECT: GRB990123 Optical Observations
DATE:    99/01/25 15:30:47 GMT
FROM:    Michel Boer at CESR-CNRS  <boer@cesr.fr>


A. Maury (Observatoire de la Cote d'Azur), M. Boer, S. Chaty (Centre
d'Etude Spatiale des Rayonnements), report:
We observed GRB 990123 from the Observatoire de la Cote d'Azur 0.9m
Schmidt Telescope. The optical counterpart of the GRB is clearly
detected as well as the host galaxy. Below are the unfiltered
magnitudes, corresponding approximately to R magnitudes, given the
detector response. The mean uncertainty is 0.4 mag. The resulting decay
slope, is 1.35, which is in good agreement with the slope mentionned by
Bloom et al. (GCN Report #208), given the uncertainties.

January
24.037037       19.68
24.052419       19.67
24.057234       20.02
24.061887       19.79
24.066539       19.71
24.071192       19.44
24.075845       20.4
24.080498       19.92
24.08515        20.05
24.094456       20.25
24.099109       20.15
24.113067       19.65
24.117731       19.82
24.122373       20.22
24.127025       20.53
24.131678       20.32
24.136331       20.49
24.140984       20.15
24.145637       19.98
24.150289       20.06
24.154942       20.44
24.159595       20.42
24.164248       20.03
24.1689         20.11
24.178206       20.23
24.182859       20.06
24.201076       20.36

Other images have been taken during the night 24-25/1/99 and will be
reported later.


[GCN OP NOTE (99/01/26 23:47 UT):  An ammended version (extra column
trailing removed and institutional affiliations added) of this circular
was added to the archive at the authors request.  The original distributed
version suffered from extraneious material from the mailer utility used
to create the posting.]