{
  "circularId": 1893,
  "eventId": "GRB 030226",
  "version": 2,
  "email": "rhoads@stsci.edu",
  "format": "text/plain",
  "bibcode": "2003GCN..1893....1R",
  "editedBy": "Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of Leo P. Singer at NASA/GSFC <leo.p.singer@nasa.gov>",
  "body": "J. E. Rhoads, J.M. Castro Cerón, J. Gorosabel, A. Fruchter, \nand C. Kouveliotou report:\n\nUsing the redshift lower limit (z > 2; Ando et al, GCNC 1884)\nand the GRB fluence (5.7e-6 erg/cm2, 30 keV < E < 400 keV; \nSuzuki et al, GCNC 1888), we can predict the time of the break\nin GRB 030226 light curve, assuming the standard burst energy\nof Frail et al (2001) (or more precisely, exploiting their empirically\ndemonstrated correlation between break time and apparent isotropic\ngamma ray energy).\n\nBased on the relations in Frail et al, we obtain\n t_jet = 10.6 days\nfor a redshift z=2.0 (and t_jet < 10.6 days for z > 2.0).\nPrior to that time the current slow decay may continue;\nthereafter a much steeper decay, t^-2 or faster, may\noccur (Rhoads 1999).\n\nThe primary uncertainty in the predicted break time arises from\nthe observed scatter in the E_isotropic - t_jet correlation.  The\nquoted one-sigma scatter in gamma ray energy in Frail et al (2001)\nis a factor of 2.  We infer a corresponding scatter of a factor\nof 2.5 in t_jet, placing a one-sigma lower limit  t_jet > 4 days.\n\nTogether with the current decay slope (0.88; Price & Warren, GCNC 1890)\nand the t=3.5 hour flux (R=18.44; Garnavich et al, GCNC 1885)\nthis suggests that the optical afterglow of GRB 030226 will be rather\nbright during the interval 1 day < t < t_jet, relative to most afterglows\nat the same observed age.  Representative fluxes using this naive\nextrapolation are\n\n       GRB age (days): 0.75  1.0   1.5   2.0   3.0   4.0   5.0  7.5   10.0\nProjected R magnitude: 20.0  20.3  20.7  20.9  21.3  21.6  21.8 22.2  22.5\n\nWe stop our projections at the nominal 10 day jet break time, and\nfurther caution even a modest steepening of the decay index early on\nwould substantially reduce the fluxes at a few days.",
  "submitter": "James Rhoads at STScI  <rhoads@stsci.edu>",
  "editedOn": 1731924401003,
  "createdOn": 1046316319000,
  "subject": "GRB 030226 : Predicted light curve"
}