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We present Follow-Up Network for Gamma-Ray Bursts (FUN GRB) Collaborationobservations of the optical afterglow of GRB 021211 made between 143 secondsand 102 days after the burst. Our unique data set includes the earliestfiltered detections and color information for an afterglow in the pre-Swiftera. We find that the afterglow is best described by (1) propagation through awind-swept medium, (2) a cooling break that is blueward of the observed opticalfrequencies, and (3) a hard electron energy distribution. However, superimposedon this "standard model" behavior we find significant chromatic variationswithin the first few hours after the burst. We consider possible reasons forthese variations, including the possibility that they are due to a dust echo.Finally, we constrain physical parameters that describe the afterglow andsurrounding medium for a variety of scenarios and find that GRB 021211'safterglow is faint for a combination of 3-4 reasons: (1) a low fraction ofenergy 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 theprogenitor, (3) a wide opening/viewing angle for the jet, and possibly (4)moderate source frame extinction. The jet appears to be significantly far fromequipartition and magnetically dominated. More extreme versions of this mightexplain the darkness of many afterglows in the Swift era.Comment: Accepted to The Astrophysical Journal, 30 pages, 5 Figures, LaTe

Early Time Chromatic Variations in the Wind‐swept Medium of GRB 021211 and the Faintness of Its Afterglow