{
  "bibcode": "2009GCN.10297....1B",
  "body": "S. D. Barthelmy (GSFC), C. B. Markwardt (GSFC/UMD), \nV. Mangano, B. Sbarufatti (INAF-IASF PA), A. Breeveld (MSSL/UCL)\nreport on behalf the Swift team:\n\nUsing the full data set from telemetry downlinks, we report\nthat Swift Trigger 381434 is due to a cosmic ray shower event\nin the BAT instrument.  It is not due to a GRB nor any other\nastrophysical source.  There were two showers ~8 msec apart\nwhich caused the 64msec trigger to fire.\n\nThe XRT observed the field of the target starting 68 s after\nthe trigger. In the initial 7 ks in PC mode no source is\ndetected within the 3 arcmin BAT error circle down to a limiting\nflux of 8 x 10^-14 erg cm^-2 s^-1. Three X-ray sources are\ndetected with more than 3 sigma significance in the whole XRT \nfield of view, the brightest one likely associated to \n1RXS J050001.1-550121, and the other two unidentified. \nAll of these sources are further than 4 arcmin from the target position.\n\nThe UVOT began settled observations of the field of the target \n65 s after the BAT trigger. No new source is detected. \nPreliminary 3-sigma upper limits using the UVOT photometric system \n(Poole et al. 2008, MNRAS, 383, 627) for the first finding chart \n(FC) exposure and subsequent exposures are:\n\nFilter         T_start(s)   T_stop(s)      Exp(s)         Mag\n\nwhite_FC            65          215          147         >21.1\nu_FC               277          526          246         >20.4\nwhite               65         1699          411         >21.6\nv                  606         1748          136         >19.4\nb                  532         1834          123         >20.3\nu                  277         1822          363         >20.6\nw1                 656         1798          136         >19.9\nm2                 631         1773          136         >19.8\nw2                 582         1551          117         >20.1\n\nThe values quoted above are not corrected for the Galactic extinction \ndue to the reddening of E(B-V) = 0.02 in the direction of the burst \n(Schlegel et al. 1998).\n\nThe lack of a bright X-ray/optical counterpart of Trigger 381434 in \nprompt observations strengthens the spurious trigger interpretation.",
  "circularId": 10297,
  "createdOn": 1262114513000,
  "email": "vanessa@ifc.inaf.it",
  "subject": "Swift Trigger 381434 is not a GRB",
  "submitter": "Vanessa Mangano at INAF-IASFPA  <vanessa@ifc.inaf.it>"
}