Central Bureau for Astronomical Telegrams
IAUC 7095: GRB 990123
The following International Astronomical Union Circular may be linked-to from your own Web pages, but must not otherwise be redistributed (see these notes on the conditions under which circulars are made available on our WWW site).
Read IAUC 7096
.dvi or
.ps format.
Circular No. 7095
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
BMARSDEN@CFA.HARVARD.EDU or DGREEN@CFA.HARVARD.EDU (science)
URL http://cfa-www.harvard.edu/iau/cbat.html ISSN 0081-0304
Phone 617-495-7244/7440/7444 (for emergency use only)
GRB 990123
Further to the item on IAUC 7094, M. Feroci and L. Piro,
Istituto di Astrofisica Spaziale, CNR, Rome; F. Frontera, Istituto
Tecnologie e Studio Radiazioni Extraterrestri, CNR, Bologna, and
University of Ferrara; V. Torroni and M. Smith, BeppoSAX Science
Operation Center, Telespazio, Rome; and J. Heise and J. in 't Zand,
Space Research Organization of the Netherlands, Utrecht, provide
the following elaboration of the information given on GCN 199 and
202: "A gamma-ray burst triggered the BeppoSAX Gamma-Ray Burst
Monitor (GRBM) on Jan. 23.40780 UT. The burst was also detected in
the Wide Field Camera (WFC) 1. The GRBM lightcurve shows a
multipeak complex structure that lasts for about 100 s with two
major peaks. The intensity of the highest peak is 11 200 counts/s
in the band 40-700 keV. A preliminary estimation of the fluence is
(3.5 +/- 0.4) x 10E-4 erg cmE-2 sE-1. This is the brightest burst
detected so far by the BeppoSAX GRBM simultaneously with the WFC.
The WFC lightcurve, which lasts for a comparable time, is also
complex, with one peak followed by a structured, higher plateau.
The WFC peak intensity corresponds to a flux of 3.4 Crab in the
energy band 1.5-26 keV, and it is reached about 40 s afterthe GRBM
peak. The position of the x-ray counterpart to GRB 990123, as
derived by the quicklook WFC image, is R.A. = 15h25m29s, Decl. =
+44o45'.5 (equinox 2000.0), with an error radius of 2' (99-percent
confidence level). A follow-up observation with BeppoSAX narrow-
field instruments is in progress."
J. Zhu and H. T. Zhang, on behalf of the Beijing Astronomical
Observatory (BAO) GRB team, write: "R-band images of the BeppoSAX
WFC error circle of GRB 990123 were obtained on Jan. 23.756 UT (8.5
hr after the GRB) with the BAO 0.6-m Schmidt telescope at Xinglong.
Due to bad weather, only one 20-min exposure image taken in thin
cloud was usable (FWHM = 6"). The central part of the image is
posted at http://vega.bac.pku.edu.cn/~zj/grb/grb990123.gif. A
faint object could be seen close to the optical candidate position
suggested by S. C. Odewahn et al. (IAUC 7094); its position from
our measurement is R.A. = 15h25m30s.28, Decl. = +44o45'59".0
(1-sigma = 0".5), with a magnitude of 19.2 (+/- 0.5?) from four
stars in the USNO-A V1.0 catalogue. The object in our image seems
slightly extended and slightly to the southwest, compared with the
discovery image of Odewahn et al., but it seems to be impossible to
confirm from only one image of poor quality. However, it could be
concluded that if such an object (in our image) is not real, the
optical transient in Odewahn et al.'s images must have faded
greatly during the 4.6-hr interval."
(C) Copyright 1999 CBAT
1999 January 23 (7095) Daniel W. E. Green
Read IAUC 7096
.dvi or
.ps format.
Our Web policy. Index to the CBAT/MPC/ICQ pages.
