{
  "bibcode": "2009GCN..9462....1S",
  "body": "B. E. Schaefer (Louisiana State), T. Guver (U Arizona), S. B. Pandey (U \nMich), report on behalf of the ROTSE collaboration:\n\nROTSE-IIIc, located at the H.E.S.S. site at Mt. Gamsberg, Namibia, \nresponded to GRB 090531B (Swift trigger 353728; J. R. Cummings et al., GCN \n9461), producing images beginning 7.3 s after the GCN notice time. An \nautomated response took the first image at 18:36:22.3 UT, 26.1 s after the \nburst, and during the gamma-ray emission, under excellent conditions. We \ntook 10 5-sec, 10 20-sec and 50 60-sec exposures. These unfiltered images \nare calibrated relative to USNO A2.0 (R). Imaging is on going.\n\nComparison to the DSS (second epoch) reveals no new sources within the \n3-sigma Swift/BAT error circle, for both single images and coadding into \nsets of 10; however, we are limited as the field is somewhat crowded. \nIndividual images have limiting magnitudes ranging from 15.3-16.0; we set \nthe following specific limits.\n\nstart UT       end UT      t_exp(s)   mlim   t_start-tGRB(s)  Coadd?\n--------------------------------------------------------------------\n18:36:22.3   18:36:27.3         5     15.3           26.1       N\n18:47:31.3   18:52:11.6       280     16.3          695.1       Y\n\n[GCN OPS NOTE(31may09):  Per author's request, the \"B\" was added\nto the burst name.]",
  "circularId": 9462,
  "createdOn": 1243797655000,
  "email": "schaefer@grb.phys.lsu.edu",
  "subject": "GRB 090531B: ROTSE-III Optical Limits",
  "submitter": "Brad Schaefer at LSU  <schaefer@grb.phys.lsu.edu>",
  "eventId": "GRB 090531B"
}