{
  "bibcode": "2009GCN.10111....1C",
  "body": "B. E. Cobb (UC Berkeley) reports:\n\nUsing the ANDICAM instrument on the 1.3m telescope at CTIO, we obtained \noptical/IR imaging of the error region of GRB 091029 (GCN 10097, Grupe et \nal.) with a mid-exposure time of 50 minutes post-burst (2009-10-29 04:43 \nUT). Total summed exposure times amounted to 36 minutes in I and 30 \nminutes in J. Imaging was done under poor (2.5\") seeing conditions.\n\nThe afterglow of GRB 091029 (e.g. GCN 10097, Grupe et al.; GCN 10098, \nFilgas et al.; GCN 10099, LaCluyze et al.) is detected in our images. \nPreliminary comparison to USNO-B1.0 stars in I and 2MASS stars in J \nindicates the following afterglow magnitudes:\n\ntime post-burst         I mag           J mag\n50 minutes              17.9+/-0.1      17.6+/-0.1\n\nIn individual I-band images, the afterglow fades by ~0.4 magnitudes \nbetween 30 and 69 minutes post-burst. During this time, the afterglow \nexhibits a shallow decay rate of alpha ~ -0.4+/-0.1 (where afterglow flux \nis proportional to t^alpha), which is consistent with the decay rate \nmeasured by LaCluyze et al. (GCN 10099).",
  "circularId": 10111,
  "createdOn": 1256859019000,
  "email": "bcobb@astro.berkeley.edu",
  "subject": "GRB 091029, SMARTS optical/IR afterglow observations",
  "submitter": "Bethany Cobb at UC Berkeley  <bcobb@astro.berkeley.edu>",
  "eventId": "GRB 091029"
}