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GCN Circular 445

BeppoSAX NFI Observation of GRB991106
1999-11-11T17:44:27Z (25 years ago)
Angelo Antonelli at Obs. Astro. di Roma <>
L.A. Antonelli, Osservatorio Astronomico di Roma;
G. Gandolfi, M. Feroci, Istituto di Astrofisica Spaziale, CNR, Rome,
D. Ricci, C. De Libero, M. Capalbi, BeppoSAX Science Operations Center, 
Telespazio, Rome; F. Frontera, Istituto Tecnologie e Studio Radiazioni 
Extraterrestri, CNR, Bologna, J. in 't Zand and J. Heise, Space Research 
Organization Netherlands, Utrecht, on behalf of the BeppoSAX Team report:

"The region of GRB 991106 (GCN #434) was observed with the Narrow 
Field Instruments (NFI) on board BeppoSAX from Nov. 6.781 to 7.565 U.T. 
(starting about 8 hrs after the burst trigger time) for a total net 
exposure time of 32 ks. In the 2-10 keV image of all data from both 
Medium-Energy Concentrator Spectrometer units 2 and 3, a faint point 
source (1 SAX J222441+5422.7) is detected, with a chance probability 
for the source being a background fluctuation of 5E-4, within the WFC 
error box (Gandolfi et al, GCN #435). The average source flux in 
2-10 keV band was (1.7+-0.4)x10E-3 counts/s corresponding to 
1.25x10E-13 erg cmE-2 sE-1, assuming a crab-like spectrum. 
The source position is R.A. = 22h24m40.8s, Dec.= +54d22'45" (Eq. 2000.0) 
and the error radius is 1'.5. 
The radio source reported by Frail (GCN #444) is 2'.1 from this X-ray 
source position and it lies outside the NFI error circle. The data do 
not allow to draw a useful constraint about the variability of this source. 
The probability of detecting a foreground source at this flux level or 
brighter in the WFC error circle is expected to be ~10% as suggested by the 
BeppoSAX LogN-LogS (Fiore et al., 1999).

This message is citable."
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