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GCN Circular 228

GRB990123, ASCA X-ray observation of afterglow
1999-01-26T15:17:19Z (25 years ago)
Toshio Murikami at ISAS <>
T. Murakami, M. Ishida and T. Dotani, Institute of Space and
Astronautical Science, and A. Yoshida and N. Kawai, Institute of
Physical and Chemical Research, report:

The X-ray astronomy satellite ASCA has been observing the X-ray afterglow
of GRB990123 since January 25.688 (UT).  The observation started about
55 hours after the burst, but the X-ray afterglow is still bright.  ASCA
will continue observing the source until January 26.806 (UT).  With only
one forth of the dataset down-linked at the tracking station, the flux
is about 1 x 10E-12 erg cmE-2 sE-1 in 2 to 10 keV assuming a power-law
with the photon index of -1.6.
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