TITLE: GCN GRB OBSERVATION REPORT NUMBER: 445 SUBJECT: BeppoSAX NFI Observation of GRB991106 DATE: 99/11/11 17:44:27 GMT FROM: 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."