M. C. Nysewander, Department of Physics and Astronomy, University of North Carolina atChapel Hill
D. E. Reichart, Department of Physics and Astronomy, University of North Carolina atChapel Hill
H.-S. Park, Lawerence Livermore National Laboratory
G. G. Williams, MMT Observatory, University of Arizona
K. Kinugasa, Gunma Astronomical Observatory
D. Q. Lamb, Department of Astronomy and Astrophysics, University of Chicago
A. A. Henden, American Association of Variable Star Observers, Clinton B. Ford Astro-nomical Data and Research Center
S. Klose, Thüringer Landessternwarte
T. Kato, Department of Astronomy, Faculty of Science, Kyoto University
A Harper, University of Chicago
H Yamaoka, Kyushu University
C Laws, University of Washington
K Torii, Department of Earth and Space Science, Graduate School of Science, 1-1 Machikaneyamacho, Toyonaka, Osaka
D G. York, University of Chicago
J C. Barentine, Apache Point Observatory
J Dembicky, Apache Point Observatory
R J. McMillan, Apache Point Observatory
J A. Moran, University of North Carolina at Chapel Hill
Dieter H. Hartmann, Clemson UniversityFollow
B Ketzeback, Apache Point Observatory
M B. Bayliss, University of North Carolina at Chapel Hill
J A. Crain, University of North Carolina at Chapel Hill
A C. Foster, University of North Carolina at Chapel Hill
M Schwartz, Tenagra Observatory
P Holvorcem, Tenagra Observatory
P A. Price, University of Hawaii
R Canterna, University of Wyoming
G B. Crew, Massachusetts Institute of Technology
G R. Ricker, Massachusetts Institute of Technology
S D. Barthelmy, NASA Goddard Space Flight Center

Document Type


Publication Date

Fall 11-10-2006

Publication Title

The Astrophysical Journal






EDP Sciences


We present Follow-Up Network for Gamma-Ray Bursts (FUN GRB) Collaboration observations of the optical afterglow of GRB 021211 made between 143 s and 102 days after the burst. Our unique data set includes the earliest filtered detections and color information for an afterglow in the pre-Swift era. We find that the afterglow is best described by (1) a propagation through a wind-swept medium, (2) a cooling break that is blueward of the observed optical frequencies, and (3) a hard electron energy distribution. However, superimposed on this ‘‘standard model’’ behavior we find, one and possibly two, significant chromatic variations during the first few hours after the burst. We consider possible reasons for these variations, including the possibility that they are due to a dust echo. Finally, we constrain physical parameters that describe the afterglow and the surrounding medium for a variety of scenarios and find that GRB 021211’s afterglow is faint for a combination of reasons: (1) a low fraction of energy in relativistic electrons, (2) a low density for the wind-swept medium, implying either a low mass-loss rate and/or a high wind velocity for the progenitor, (3) a wide opening/viewing angle for the jet, and possibly (4) moderate source-frame extinction. The jet appears to be significantly far from equipartition and magnetically dominated. More extreme versions of this might explain the darkness of many afterglows in the Swift era.


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