GCN Circular 4071
M. Perri, M. Capalbi (ASDC), D.N. Burrows (PSU) report on behalf of the Swift XRT team: XRT began observing the field at 17:23:52 UT, about 50 minutes after the BAT trigger. The on-board centroiding algorithm did not converge on a source, so no prompt X-ray position is available. However, the downlinked lightcurve shows evidence for a fading X-ray source in the field of view. There are no catalogued X-ray sources in the field, indicating that this source is the GRB afterglow. Further analysis will require processing of the XRT full telemetry data following the next ground station contact.