{
  "bibcode": "2015GCN.18393....1D",
  "body": "M. De Pasquale (UCL-MSSL) and S. B. Cenko (GSFC)\nreport on behalf of the Swift/UVOT team:\n\nThe Swift/UVOT began settled observations of the field of\nthe trigger 657564 (possible GRB 151004A) 3613 s after the\nBAT trigger (Cenko et al., GCN Circ. 18389).\nNo optical afterglow consistent with the BAT position\nis detected in the initial UVOT exposures.\nPreliminary 3-sigma upper limits using the UVOT photometric system\n(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first\nfinding chart (FC) exposure and subsequent exposures are:\n\nFilter         T_start(s)   T_stop(s)      Exp(s)         Mag\n\nwhite_FC          3613         3763          147         >20\nwhite             3613         4994          344         >20.3\nv                 3770         5404          393         >18.7\nb                 4590         4789          197         >19.2\nu                 4384         4584          197         >18.9\nw1                4179         4379          197         >19.0\nm2                3974         5565          350         >19.3\nw2                5000         5200          197         >19.1\n\nThe magnitudes in the table are not corrected for the heavy Galactic\nextinction due to the reddening of E(B-V) = 1.03 in the direction of\nthe burst (Schlegel et al. 1998).\n\n-- \n\nDr. Massimiliano De Pasquale\nResearch associate - Swift UVOT scientist\nMullard Space Science Laboratory, University College London",
  "circularId": 18393,
  "createdOn": 1444047204000,
  "email": "m.depasquale@ucl.ac.uk",
  "subject": "Trigger 657564 / GRB 151004A: Swift/UVOT Upper Limits",
  "submitter": "Massimiliano de Pasquale at IASF-Palermo  <m.depasquale@ucl.ac.uk>",
  "eventId": "GRB 151004A"
}