TITLE: GCN CIRCULAR NUMBER: 6003 SUBJECT: GRB070107: Swift/XRT refined analysis DATE: 07/01/08 22:12:04 GMT FROM: Teresa Mineo at INAF-IASFA T. Mineo, B. Sbarufatti, V. Mangano, G. Cusumano (INAF-IASF Pa) report on behalf of the Swift XRT team: We have analyzed the first ten orbits of Swift-XRT data on GRB 070107 (Stamatikos et al. GCN 5999), with a total exposure of 420 s seconds in Window Timing (WT) mode and 15.8 ks seconds in Photon Counting (PC) mode. This provides a refined XRT position at RA,Dec=159.4016,-53.2131 which is: RA (J2000) = 10h 37m 36.4s Dec(J2000) = -53d 12m 47.3s with an estimated error radius of 3.7 arcseconds (90% confidence). This position is 59.4 arcseconds from the BAT refined position (Barthelmy et al. GCN 6001), 2.6 arcseconds from the initial XRT position (Kennea & Stamatikos, GCN 6000), and 0.4 arcseconds from the UVOT optical candidate (Boyd et al., GCN 6002). The 0.3-10 keV X-ray light curve presents a bright flare starting at about 300 s from the trigger and coincident with the peak detected in the BAT light curve (Barthelmy et al. GCN 6001). A second fainter peak is also present at 1300 s and the light curve between 3 ks and 59 ks can be fit with a simple power-law with a decay slope of 1.05 ± 0.05. The X-ray spectrum from the XRT/WT data, mainly covering the first bright flare, is well fit by an absorbed power-law with a photon index of 2.07±0.07 and column density of (3.8±0.2)e21 cm**-2, consistent with the Galactic column density in the direction of the source (3.6E21 cm**-2). The unabsorbed 0.3-10 keV flux for this spectrum is 1.3e-9 erg/cm**2/s. The XRT/PC data is modeled by an absorbed power law with a photon index of 2.2±0.1 and column density of (4.3±0.4)e21 cm**-2 and the unabsorbed 0.3-10 keV flux is 2.48E-11 erg/cm**2/s. Assuming the X-ray emission continues to decline at the same rate, we predict a 0.3-10 keV XRT count rate of 1e-2 count/s at T+48hr, which corresponds to an observed 0.3-10 keV flux of 1.4e-12 erg/cm**2/s. This circular is an official product of the Swift XRT Team.