{
  "bibcode": "2016GCN.19530....1D",
  "body": "M. De Pasquale (UCL-MSSL) and D. Malesani (DARK/NBI)\nreport on behalf of the Swift/UVOT team:\n\nThe Swift/UVOT began settled observations of the field of GRB 160611A\n2687 s after the BAT trigger (Malesani et al., GCN Circ. 19522).\n\nVery close to the XRT error circle (Osborne et al. GCN Circ. 19523), two\nsources are detected in the UVOT images. These sources are also detected\nin the Digitized Sky Survey (DSS) and are listed in the USNO catalog.\nTheir light would blend with any new source at the XRT position, making\nthe analysis more delicate.\n\nNone of the two sources shows any significant flux decrease in the white\nfilter between the first two white exposures (mid-time: 3071 s after\nthe trigger) and the last three white exposures (mid-time: 10030 s after\nthe trigger). Similarly, we find no significant decrease of the flux\nof the two sources in the u filter between the first u filter exposure\n(mid-time: 2946 s) and the last one (mid-time: 8560 s).\nWe conclude that no optical afterglow consistent with the XRT position\nis detected in the UVOT exposures.\n\nPreliminary 3-sigma upper limits using the UVOT photometric system\n(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) are:\n\nFilter         T_start(s)   T_stop(s)      Exp(s)         Mag\n\nwhite             2687         3456          344         >19.6\nwhite             9578        10478          880         >19.8\nv                 3668         3867          197         >18.1\nb                 3051         9573         1082         >18.9\nu                 2846         8660          393         >19.6\nw1                4078         5167          191         >19.7\nm2                3873         4072          197         >19.4\nw2                3463        10905          611         >20.6\n\nThe magnitudes in the table are not corrected for the Galactic extinction\ndue to the reddening of E(B-V) = 0.22 in the direction of the burst\n(Schlegel et al. 1998).",
  "circularId": 19530,
  "createdOn": 1465757545000,
  "email": "m.depasquale@ucl.ac.uk",
  "subject": "GRB 160611A: Swift/UVOT observations",
  "submitter": "Massimiliano de Pasquale at IASF-Palermo  <m.depasquale@ucl.ac.uk>",
  "eventId": "GRB 160611A"
}