{
  "bibcode": "2018GCN.23121....1D",
  "body": "V. D���Elia (SSDC), A. D���A�� (INAF-IASFPA), F. E. Marshall (NASA/GSFC), A. Y. Lien (GSFC/UMBC) and M. J. Moss (George Washington University)\nreport on behalf of the Swift team:\n\nWe analysed the full Swift dataset for the possible burst which triggered BAT (Trigger 852625, Moss et al., GCN Circ. 23115).\n\nThe BAT ground analysis uses data from T-60 to T+243 sec. The BAT image significance is only 4.9 sigma (15-350 keV).  Also, the mask-weighted light curve does not show anything significant. \n\nThe XRT data consist of 2.64 ks and are entirely in PC mode. No new X-ray source is found inside the BAT error region, down to a limit of ~0.001 cts/s, corresponding to a 0.3-10 keV observed flux of ~4e-14 erg cm^-2 s^-1 (assuming a typical GRB spectrum) The results of the XRT-team automatic analysis of the XRT observations, including a position-specific upper limit calculator, are available at http://www.swift.ac.uk/possible_GRBs/00852625/index.php\n\nThe Swift/UVOT began settled observations 154 s after the BAT trigger. No optical afterglow consistent with the BAT position is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposures are:\n\nFilter         T_start(s)   T_stop(s)      Exp(s)         Mag\nwhite_FC           154          304          147         >19.9\nu_FC               312          562          246         >19.2\n\nWe thus conclude that this trigger was just a noise fluctuation.\n\nThis circular is an official product of the Swift team.",
  "circularId": 23121,
  "createdOn": 1533923541000,
  "email": "valerio.delia@ssdc.asi.it",
  "subject": "Swift Trigger 852625: Swift/BAT/XRT/UVOT observations",
  "submitter": "Valerio D'Elia at ASDC  <valerio.delia@ssdc.asi.it>"
}