TITLE: GCN CIRCULAR NUMBER: 6610 SUBJECT: Swift XRT observation of GRB 070707 DATE: 07/07/08 18:53:29 GMT FROM: Andy Beardmore at U Leicester A.P. Beardmore, K.L. Page (U. Leicester) and A. Parsons (GSFC) report on behalf of the Swift XRT team: On 2007 Jul 08 00:57:50UT the Swift XRT started observing the field of the INTEGRAL burst GRB 070707 (Beckmann et al., GCN 6606; Gotz et al., GCN 6607). In a 3.8ks exposure photon counting mode image taken from 31.8 ks to 54.1 ks after the trigger, we detect a source at RA, Dec = 267.7437, -68.9242, which is RA(J2000) = 17h 50m 58.49s Dec(J2000) = -68d 55m 27.0s with an uncertainty of 5.4 arcsec (90% containment). This is 36.3 arcsec from the position reported by Gotz et al. (GCN 6607), and within their error circle. Using a circular extraction region of 10 pixels radius, we observe 26 total counts. Together with an estimated background level of 1.0 count in the extraction region, we find the 99.73% Bayesian confidence level on the source count rate is 0.003 to 0.011 count s^-1. However, with such a limited number of photons, it is impossible to say at this stage whether the source is fading and if this is the X-ray counterpart to the GRB. This circular is an official product of the Swift XRT team.