GCN Circular 6659
K.L Page (U. Leicester) and H. Ziaeepour (UCL-MSSL) report on behalf of the Swift-XRT team: We have analysed the first three orbits of Swift-XRT data obtained for GRB 070724 (Ziaeepour et al., GCN Circ. 6654), which includes ~60 s of Windowed Timing (WT) mode data and ~5.2 ks of Photon Counting (PC) data. Using 399 s of overlapping XRT PC mode and UVOT V-band data, we find an astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue) of RA, Dec (J2000) = 27.80815, -18.59448 which is equivalent to: RA (J2000): 01 51 13.96 Dec (J2000): -18 35 40.1 with an uncertainty of 2.2 arcsec (radius, 90% confidence). This is 2.7 arcsec from the initial XRT position (GCN Circ. 6654) and 77.8 arcsec from the ground-calculated BAT position (Parsons et al., GCN Circ. 6656). The first orbit of XRT data shows flaring activity, with the underlying power-law decay asserting itself from about 500 seconds after the trigger. This decay slope is poorly constrained with the data currently available: alpha ~ 0.4 +0.3/-0.2 Fitting the PC data from the second and third orbits (~4-12 ks after the trigger) in order to avoid any spectral evolution during the flares, the spectrum can be modelled by a power-law of Gamma = 1.3 +0.8/-0.6, absorbed by the Galactic column in this direction of 1.43e20 cm^-2. The 0.3-10 keV observed (unabsorbed) flux during this time is 5.18e-13 (5.27e-13) erg cm^-2 s^-1. If the decay continues with a slope of alpha ~ 0.4, the count rate at 24 hours is predicted to be 4e-3 count s^-1; this ranges between 2e-3 and 8e-3 count s^-1, taking into account the uncertainties on the slope. Using the spectral fit detailed above, this corresponds to an observed flux of (2 +7/-1)e-13 erg cm^-2 s^-1 (over 0.3-10 keV). This circular is an official product of the XRT team.