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GCN Circular 209

GRB990123, Optical observation
1999-01-24T13:26:03Z (25 years ago)
Luciano Nicastro at IFCAI-CNR <>
GRB990123 Optical Observation at SAO-RAS

V. Sokolov, S. Zharikov (SAO-RAS) and L. Nicastro, M. Feroci, E. Palazzi
on behalf of the BeppoSAX team report:

We obtained an R-band image of the BeppoSAX localization of GRB990123
on 1999 Jan 24.076 UT, 16.04 hours after the GRB event, with the SAO-RAS
6-m telescope.  The weather was cloudy.
In spite of that, in a 15-min exposure image we were able to see an
object at the position of the optical candidate suggested by Odewahn et al.
(GCN #201).  We estimated a magnitude of 19.6 +/- 0.2 (using star 1 from
GCN #204) and 19.9 +/- 0.2 (using star 2 from GCN #204).
These values include the contribution of the proposed underlying host
galaxy.  To have the contribution of the OT alone these value should be
increased by about 0.25 magnitudes.

R = 19.9 +/- 0.2 is compatible with the power-law decay with index
-1.5 found by Bloom et al. (GCN #208) as we would expect to find
about R = 20.1 using the R = 18.2 on Jan 23.565 UT and R = 21.3 for the
underlying galaxy (GCN #201).

This report may be cited.

[GCN OP NOTE:  This circular was actually received at 12:40:01 UT, but was 
delayed in distribution due to the submitter not having prior vetting.]
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