TITLE:   GCN CIRCULAR
NUMBER:  11222
SUBJECT: GRB 100905A: UKIRT zJHK Observation
DATE:    10/09/06 04:55:03 GMT
FROM:    Myungshin Im at Seoul Nat U  <mim@astro.snu.ac.kr>

  Myungshin Im, Changsu Choi, Hyunsung Jun, Eugene Kang (CEOU/Seoul
  National University), Y. Urata (NCU), P. Choi (Pomona College),
  T. Sakamoto (NASA/GSFC), and N. Gehrels (NASA/GSFC) on behalf
  of a larger collaboration

   We observed GRB 100905A (Marshall et al. GCN 11214) in z, J, H,
  and K filters using UKIRT. The observation started at Sept. 05,
  15:22 UT or roughly 17 minutes after the BAT alert, until the
  sunrise.
   The reduced images with non-optimal calibration frames show
  a "possible" very faint source within the XRT error circle
  (Evans et al. GCN 11219) whose significance is only 2-3 sigma
  in each image (2-sigma limit, J=19.8, H=19.0,
  and K=18.7 mag). The faint smudge show up in all zJHK filter
  images, suggesting this could be an afterglow, but we do not
  exclude the possibility that this is just a spurious detection.
   Further analysis of the UKIRT data is ongoing.