{
  "bibcode": "2015GCN.18131....1K",
  "body": "N. P. M. Kuin (UCL-MSSL) and P. A. Evans (U Leicester)\nreport on behalf of the Swift/UVOT team:\n\nWe report further on the Swift/UVOT observations of GRB 150811A which\nbegan 148 s after the BAT trigger (Evans et al., GCN Circ. 18119).\nA source consistent with the XRT position (Goad et al. GCN Circ. 18124)\nwas reported earlier in the optical/ir by Butler et al.(GCN Circ. 18120)\nZheng et al. (GCN Circ. 18121), Kuin et al.(GCN Circ. 12122), Japelj et\nal., (GCN Circ. 12123),  Perley and Cenko (GCN. Circ. 12125), Moskivitin\n(GCN Circ. 12128). Our initial observations in the white filter show a\nrise from the start at 147s around magnitude (white) 21 which continues\nin the u band event data and starts leveling off around magnitude 17.8\n550s after the trigger, consistent with the report by Perley and Cenko.\nThe data taken during the next orbit show that  the decay had already\nset in. The uv bands showed marginal count rates in all three bands\ninitially below the 3-sigma level, suggesting the burst is at low redshift.\n\n\nPreliminary detections and 3-sigma upper limits using the UVOT photometric\nsystem (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early\nexposures are:\n\nFilter         T_start(s)   T_stop(s)      Exp(s)           Mag\n\nwhite_FC           148          297          147         20.39 +/- 0.23\nu_FC               306          549          239         18.19 +/- 0.11\nwhite             4424         4624          197         19.16 +/- 0.07\nu                 5449         5854          197         18.83 +/- 0.16\nv                 4835         5034          197         18.89 +/- 0.17\nb                 4219         4419          197         19.31 +/- 0.14\nw1                5244        11888         1082        >20.6\nm2                5039        10981         1082        >21.1\nw2                4630         6265          393        >20.5\n\nThe magnitudes in the table are not corrected for the Galactic extinction\ndue to the reddening of E(B-V) = 0.17 in the direction of the burst\n(Schlegel et al. 1998).",
  "circularId": 18131,
  "createdOn": 1439381683000,
  "email": "npkuin@gmail.com",
  "subject": "GRB 150811A: Swift/UVOT further observations",
  "submitter": "Paul Kuin at MSSL  <npkuin@gmail.com>",
  "eventId": "GRB 150811A"
}