TITLE: GCN CIRCULAR NUMBER: 11316 SUBJECT: Refined analysis shows Swift Trigger 435520 is not a GRB DATE: 10/10/03 22:14:53 GMT FROM: Scott Barthelmy at NASA/GSFC S. Barthelmy (GSFC), J. Kennea (PSU), and R. Margutti (INAF-OAB) report on behalf of the Swift team: Using the full data set (T-64 to T+240 sec) from the recent downlink, refined ground analysis shows that the Swift-BAT trigger 435520 (Cummings, et al., Circ 11315) is due to a chance fluctuation in the image domain. It is not a GRB, nor anything astrophysical. Swift-XRT obtained 1.5 ks of Photon Counting (PC) mode data, from T0+160 s to T0+1.7 ks. No source is found in the BAT error circle, with a 3-sigma upper limit of 6.7 x 10-3 ct/sec; for a typical GRB, this would correspond to an upper limit on the observed 0.3-10 keV flux of 3.4 x 10-13 erg cm-2 s-1.