BeppoSAX MAIL n. 99/1: ALERT for GB990123 - "The mighty" :)
On Jan.23, 9:47:14 UT BeppoSAX GRBM has been triggered by a burst, GB990123 (also BATSE trigger n.7343), the strongest detected so far simultaneously with the WFC.Preliminary coordinates from WFC are: R.A.(2000)= 231.374 DEC(2000)= +44.754 with an error radius of about 5'
A follow-on with NFI is being planned
BeppoSAX Mission Scientist
BeppoSAX MAIL n. 99/3: GRB990123: X-ray afterglow
A BeppoSAX follow-up of GRB990123 initiated around 15:40 UT, i.e. 6 hr after the burst
Preliminary analysis of the first 20 minutes of the data at SOC shows a previously unknown strong source (about 10**-11 c.g.s in the 1.6-10 keV ) in the center of the WFC error circle.Preliminary coordinates are: R.A.(2000)= 231.374 DEC(2000)= +44.758
The error radius is 1.5'
Considering its strenght, this X-ray source is very likely the X-ray afterglow of GB990123 We will continue to observe it to monitor its temporal evolution
BeppoSAX Mission Scientist
Link to the GRB 990123 page (optical counterpart, ROTSE detection of the optical peak)
Another optical flash expected!?
I am writing about GRB 990123. This gamma-ray burst was apparently accompanied by an optical flash that reached 8th mag a few seconds after the burst on 1999 Jan 23, for a duration of 5 or more seconds, as detected by the Robotic Optical Transient Search Experiment (ROTSE; http://www.umich.edu/~rotse/) at Los Alamos, New Mexico, USA. Several hours later the optical transient was seen at 18th mag from Palomar Observatory. The J2000 position is 15:25:30.34, +44:45:59.1 according to the Palomar observers. An absorption-line redshift of 1.61 has been obtained from Keck spectra.
An exciting aspect of this object is the suggestion by S. G. Djorgovski et al. that GRB 990123 was gravitationally lensed (which might account for the extraordinary apparent luminosity). This raises the possibility, emphasized by E. Turner, that the gamma-ray and optical bursts may recur in the next few days to months, due to lensing time delays along different paths to the Earth.
It would thus be very worthwhile for vsnet observers to monitor this position constantly, even with small telescopes or binoculars, to search for such repeated optical transients, which could in principle even reach to brighter than 8th mag for a few seconds depending on the lensing amplification. Precise times, magnitude estimates, and other details should be determined for any flashes that are seen.
Howard E. Bond
Space Telescope Science Institute
GSC-based wide-field charts
USNO A1.0-based close-up (with estimated V magnitudes)
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