{
  "bibcode": "2013GCN.14374....1C",
  "body": "B. E. Cobb (GWU), reports:\n\nUsing the ANDICAM instrument on the 1.3m telescope at CTIO, we\nobtained optical/IR imaging of the error region of GRB 130408A\n(GCN 14361, Lien et al.)  over several epochs (with mid-exposure\ntimes of 2013-04-09 00:30 UT, 02:15 UT, 03:41 UT and 2013-04-11\n02:24 UT). For each epoch, several dithered images were obtained with\ntotal summed exposure times of 15 min in V and I and 12 min in J\nand K.  For the final epoch, total exposure times were 36 min in I\nand 30 min in J.\n\nThe fading afterglow of GRB 130408A (e.g. GCN 14362, Melandri et al.;\nGCN 14363, Siegel et al.; GCN 14364, Sudilovsky et al.) was detected\nwith the following magnitudes (or 3-sigma limits):\n\nmid-exposure\ntime\n(hours)           I mag             J mag            K mag\n2.64611         18.8 +/- 0.1    17.8 +/- 0.1     > 16.1\n4.38444         19.6 +/- 0.1    18.6 +/- 0.2    16.8 +/- 0.2\n5.82472         20.0 +/- 0.1    18.6 +/- 0.2     > 17.2\n52.53694        > 21.5            > 19.6            ...\n\n(Optical photometry is calibrated against USNO-B1.0 stars\nand IR photometry is calibrated against 2MASS stars in the field.)\n\nBetween about 2.6 hrs and 5.8 hrs post-burst, the GRB afterglow fades\nwith a decay rate of approximately alpha = 1.4 (where afterglow flux is\nproportional to t^-alpha).",
  "circularId": 14374,
  "createdOn": 1365799597000,
  "email": "bcobb@gwu.edu",
  "subject": "GRB 130408A: SMARTS optical/IR afterglow observations",
  "submitter": "Bethany Cobb at GWU  <bcobb@gwu.edu>",
  "eventId": "GRB 130408A"
}