GCN Circular 17902
V. D'Elia (ASDC), S. D. Barthelmy (GSFC), P. A. Evans (U. Leicester), L. Izzo (URoma/ICRA) and M. H. Siegel (PSU) report on behalf of the Swift team: We have analysed 4.5 ks of Swift/XRT data for the Swift/BAT-detected possible burst GRB 150604A (D'Elia et al. GCN Circ. 17901), collected in Photon Counting mode, between 138 s and 21.6 ks after the BAT trigger. No X-ray sources have been detected inside or close to the Swift/BAT error region. The 3-sigma upper limit at the Swift/BAT position is ~0.002 ct s^-1, corresponding to a 0.3-10 keV observed flux of ~1e-13 erg cm^-2 s^-1 (assuming a typical GRB spectrum). Ground analysis of the BAT data for this trigger shows that the significance of the initial detection has dropped below that considered to be a valid trigger. Swift/UVOT began settled observation of the field 142 s after the BAT trigger. No new source is detected in the initial 1.4 ks of observation down to a white magnitude limit of 20.9. Therefore, this trigger is likely due to noise, and not due to anything astrophysical. This circular is an official product of the Swift team.