{
  "bibcode": "2008GCN..7609....1C",
  "body": "B. E. Cobb (Yale), 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 080413a\n(GCN 7594, Beardmore et al.), starting at 2008-04-13 05:48 UT,\nwhich is ~2.9 hours post-burst. Several dithered images were obtained\nin each filter, with total summed exposure times of 180s in each of\nBRIYJK and 120s in each of H and V.\n\nThe GRB afterglow (GCN 7593 Rykoff & Rujopakarn; GCN 7594,\nBeardmore et al.) is detected in all our images.  At\na mid-exposure time of 2008-04-13 06:02 (~3.1 hours post-burst)\nthe afterglow has the following magnitudes (which have not been\ncorrected for Galactic reddening):\n\nB= 20.88 +/- 0.10\nV= 20.25 +/- 0.11\nR= 19.25 +/- 0.05\nI= 18.84 +/- 0.06\nJ= 18.23 +/- 0.23\nH= 17.05 +/- 0.15\nK= 16.19 +/- 0.12\n\nOptical photometry is calibrated against Landolt standard stars\nand IR photometry is calibrated against 2MASS stars in the field.\n\nBetween 3.1 and 5.1 hours post burst, the afterglow decays\nby ~0.75 magnitudes, indicating an approximate decay rate of alpha = -1.4\n(where afterglow flux is proportional to t^alpha).",
  "circularId": 7609,
  "createdOn": 1208114558000,
  "email": "cobb@astro.yale.edu",
  "subject": "GRB 080413a, SMARTS optical/IR afterglow observations",
  "submitter": "Bethany Cobb at Yale U  <cobb@astro.yale.edu>",
  "eventId": "GRB 080413A"
}