{
  "bibcode": "2013GCN.14701....1B",
  "body": "S. D. Barthelmy (GSFC), A. P. Beardmore (U Leicester),\nH. A. Krimm (CRESST/GSFC/USRA), and M. H. Siegel (PSU)\nreport on behalf of the Swift Team:\n\nWe conclude that subthreshold trigger #556533 (Beardmore, et al.,\nGCN Circ. 14699) was caused by a cosmic ray shower and chance\ncoincidence and is not due to a GRB or other astrophysical phenomenon.\n\nUsing the data set from T-240 to T+963 sec from the recent telemetry\ndownlink, we report that the full Swift/BAT event data shows no\nsignificant features in the light curve.\n\nThe Swift/XRT began settled observations of the field of trigger #556533\n155 s after the BAT trigger. There is nothing visible in the XRT\ndata at the position of the BAT onboard error circle, or in the entire image.\nThe XRT upper limit is 0.01 c/s in 614 s of PC mode data.\n\nThe Swift/UVOT began settled observations of the field of trigger #556533\n155 s after the BAT trigger. No optical afterglow consistent with the BAT\nposition is detected in the initial UVOT exposures. Preliminary 3-sigma\nupper limits using the UVOT photometric system (Breeveld et al. 2011,\nAIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposure and\nsubsequent exposures are:\n\nFilter         T_start(s)   T_stop(s)      Exp(s)         Mag\n\nu_FC               155          405          246         >19.7\nv                  460          629           39         >18.3\nb                  410          724           55         >19.1\nu                  155          703          285         >19.7\nw1                 510          678           39         >18.2\nw2                 584          604           19         >17.9\n\nThe magnitudes in the table are not corrected for the Galactic extinction\ndue to the reddening of E(B-V) = 0.85 in the direction of the burst\n(Schlegel et al. 1998).",
  "circularId": 14701,
  "createdOn": 1369404290000,
  "email": "hans.krimm@nasa.gov",
  "subject": "Swift Trigger 556533 is not an astrophysical event",
  "submitter": "Hans Krimm at NASA-GSFC  <hans.krimm@nasa.gov>"
}