{
  "bibcode": "2003GCN..2064....1L",
  "body": "Weidong Li, Ryan Chornock, Saurabh Jha, and Alexei V. Filippenko (UC Berkeley)\nreport:\n\nWe selected from the GCN literature all available R-band measurements of\nthe GRB 030329 afterglow. We fitted a smoothly broken power-law model\n(Beuermann et al. 1999, A&A 352, L26; Stanek et al. 2001, ApJ 563, 592)\nto the data within 24 hours of the burst, and obtained the following\nparameters: alpha_1 = -0.75 +/- 0.06, alpha_2 = -1.90 +/- 0.05, t_break\n= 0.44 +/- 0.04 days, and s = 5 +/- 2. Our fitting parameters are similar\nto those reported by Zeh et al. (GCN 2047) except for alpha_2 (ours is much \nsteeper). A plot showing the fit can be found at\n\nhttp://astron.berkeley.edu/~bait/grb/grb030329.fit.ps\n\nwhile a table of GCN R-band photometry of GRB 030329 can be found at\n\nhttp://astron.berkeley.edu/~bait/grb/gcn030329.r.dat\n\nwhich includes citations for all the data points used in the plot.\n\nThe substantial re-brightening reported by Lipkin et al. (GCN 2045) and\nBurenin et al (GCN 2046) is apparent in the plot. Applying the above fitting\nparameters to epochs after t = 24 hours, we found that the residual component\nbrightened steeply starting from t = 22 hours and reached a peak of 16.8 mag\nat t = 40 hours, then declined gradually thereafter. Attempts to fit this\ncomponent with the R-band light curve of the hypernova SN 1998bw all failed;\nthus the re-brightening may not be caused by a SN component.\n\nAnalysis of the color of the GRB from KAIT photometry during this phase\nsuggests the afterglow has a roughly constant color of (B-V) = 0.26 +/-\n0.02 mag, (V-R) = 0.36 +/- 0.02 mag, and (V-I) = 0.78 +/- 0.02. (The data\nof Fitzgerald & Orosz, GCN 2056, suggests a constant (B-V) = 0.39 +/- 0.02\nmag; there is an offset from the KAIT B photometry, perhaps due to a color\nterm). The constant color during the phase of the re-brightening is additional\nevidence against a SN component explanation, in which significant color\nchanges are expected when the SN rises to the maximum.\n\nDensity inhomogeneities and extra energy sources are possible explanations \nfor the re-brightening. \n\nThis message may be cited.",
  "circularId": 2064,
  "createdOn": 1049236323000,
  "email": "weidong@astron.berkeley.edu",
  "subject": "GRB 030329: fitting parameters and re-brightening",
  "submitter": "Weidong Li at UC Berkeley KAIT/LOSS  <weidong@astron.berkeley.edu>",
  "eventId": "GRB 030329"
}