TITLE: GCN CIRCULAR NUMBER: 18423 SUBJECT: GRB 151004A: Swift-XRT follow-up observations DATE: 15/10/16 13:25:03 GMT FROM: Claudio Pagani at U of Leicester C. Pagani, K. L. Page, P. A. Evans (U. Leicester) and S. B. Cenko (GSFC) report on behalf of the Swift-XRT team: A second epoch of XRT data was collected on the field of the Swift Trigger 657564 / GRB 151004A (Cenko et al., GCN Circ. 18389) on 2015 October 15. The observations consist of 7.7 ks of PC mode data, from T0+885 ks to T0+932 ks. The candidate X-ray source reported in Barthelmy et al., GCN Circ. 18396, originally detected at a count rate of 4.8 (+/- 1.14) x 10^-3 cnts/sec (0.3-10 keV) is not detected in this second epoch of observations, with a 3 sigma upper limit of 1.5 x 10^-3 cnts/sec (0.3-10 keV). The fading confirms that this is the X-ray afterglow of the Swift Trigger 657564 / GRB 151004A. This circular is an official product of the Swift-XRT team.