GCN Circular 5992
Vanessa Mangano, Boris Sbarufatti, Teresa Mineo (INAF-IASFPA) report on behalf of the Swift XRT team: We analysed the first seven orbits of XRT data of GRB070103 (Sakamoto et al., GCN 5988) consisting of 12 ks of exposure in Photon Counting (PC) mode in the time interval form 100 s to 30 ks from the trigger. The refined position of the source is RA (2000) = 23h 30m 13.90s Dec (2000) = +26d 52' 34.17" with an uncertainty of 3.7 arcsec (90% containment). This is 4.1 arcsec from the preliminary XRT position and 3.44 arcmin form the refined BAT position (Barbier et al., GCN 5991). The 0.3-10 keV X-ray light curve shows an initial flare peaking at about 500 s from the trigger, followed (after the first orbital gap) by a power law decay with slope -1.4 +/- 0.1 up to 30 ks. If decaying at the present rate the source will reach a count rate level of 1.5e-3 counts/s (corresponding to flux level of 1.e-13 erg cm^-2 s^-1) at T+24 hr. The PC spectrum is well fit by an absorbed power law with photon index 2.3 +/- 0.1 and N_H (3.2 +/- 0.7) e21 cm^-2 in excess with respect to the Galactic value of 5.0e20 cm^-2. The average 0.3-10 keV unabsorbed flux during the observation is 3.8e-12 erg cm^-2 s^-1. This circular is an official product of the Swift XRT team.