TITLE:   GCN CIRCULAR
NUMBER:  17902
SUBJECT: Swift trigger 642453 is not an astrophysical source
DATE:    15/06/04 14:58:01 GMT
FROM:    Valerio D'Elia at ASDC  <delia@asdc.asi.it>

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.