{
  "bibcode": "2007GCN..6829....1C",
  "body": "B. E. Cobb, part of the larger SMARTS consortium, reports:\n\nUsing the ANDICAM instrument on the 1.3m telescope at CTIO, we\nobtained optical/IR imaging of the error region of GRB 070911\n(Krimm et al. GCN 6777) with the following mid-exposure times:\n         2007-09-13 07:10:30 UT -  2.05 days post-burst\n         2007-09-15 06:42:00 UT -  4.03 days post-burst\n         2007-09-22 05:22:21 UT - 10.98 days post-burst\nFor each observation, total summed exposure times amounted to\n36 minutes in I and 30 minutes in J.\n\nA fading afterglow is detected in both I and J within the X-ray afterglow\nerror region (Stratta et al. 6779). This afterglow has the following \ncoordinates and magnitudes:\n\nRA/DEC: 01:43:14.4 -33:29:02.5\n\ndays post\nburst           I-magnitude (or limit)  J-magnitude (or limit)\n----------------------------------------------------------------\n  2.05           20.9 +/- 0.1            19.8 +/- 0.2\n  4.03           21.9 +/- 0.2           >19.5 +/- 0.1\n10.98          >22.3 +/- 0.1           >19.7 +/- 0.1\n\nThe I-band photometry is calibrated to a number of secondary stars in the\nfield of GRB 070911.  The magnitude of these secondary stars was\nderived using Landolt standard star observations obtained\nduring the first two epochs, which were photometric night at CTIO.\nThe J-band images are calibrated based on several 2MASS stars in the \nfield.\n\nThe afterglow's behavior between the first two epochs is consistent with a\ndecay rate of alpha = -1.4+/-0.3.  Interestingly, no J-band afterglow was\ndetected by Butler et al. (GCN 6780) to J > 16.5 only 3 hours after\nthe burst. This indicates that a period of rebrightening might have \noccurred between 3 hours and 2 days post-burst, though steady decay\nis only ruled out at the ~1 sigma level.",
  "circularId": 6829,
  "createdOn": 1190925599000,
  "email": "cobb@astro.yale.edu",
  "subject": "GRB 070911, SMARTS optical/IR afterglow observations",
  "submitter": "Bethany Cobb at Yale U  <cobb@astro.yale.edu>",
  "eventId": "GRB 070911"
}