{
  "bibcode": "2002GCN..1754....1C",
  "body": "R. Chornock, W. Li, A. V. Filippenko, and S. Jha, University of\nCalifornia, Berkeley report:\n\nWe have further analysed the unfiltered KAIT dataset (GCN 1737) for the \nafterglow associated with GRB 021211 (GCN 1731).  The data show a\nsteeply declining light curve, falling from magnitude 14.8 to mag 19.0\nin the first half hour after the burst. It is apparent that the light\ncurve underwent an early break.  A fit to our first nine data points,\nspanning the time interval of 2.2-6.5 minutes after the GRB, shows a\ndecay with a power-law index of -1.60 +/- 0.02.  The light curve then\nshows a break at about 12 minutes after the burst.  A fit to later\ndata, taken 20 to 150 minutes after the GRB, gives a slope of \n-0.96 +/- 0.04, consistent with the decay seen in concurrent\nobservations by Price and Fox (GCN 1733).\n\nThis break from a steep initial decline to a shallow later decline is \nreminiscent of the early behavior of GRB 990123 (Akerlof et al. 1999, \nNature, 398, 400).  The early emission in that object is believed to\nbe due to the reverse shock, while the later emission is ascribed to\nthe normal forward shock (Sari and Piran 1999, ApJ, 517, L109).  We\nhypothesize that our data for GRB 021211 show a similar evolution for\nthis object, but it is substantially fainter (~5 mags) than 990123 at\nsimilar epochs.\n\nThis message may be cited.",
  "circularId": 1754,
  "createdOn": 1039811667000,
  "email": "chornock@astro.berkeley.edu",
  "subject": "GRB 021211: early break in light curve",
  "submitter": "Ryan Chornock at UC Berkeley  <chornock@astro.berkeley.edu>",
  "eventId": "GRB 021211"
}