The unusual optical afterglow of the gamma-ray burst GRB 021004: Color changes and short-timescale variability

D. Bersier, K. Z. Stanek, J. N. Winn, T. Grav, M. J. Holman, T. Matheson, B. Mochejska, D. Steeghs, A. R. Walker, P. M. Garnavich, J. Quinn, S. Jha, K. H. Cook, W. W. Craig, P. J. Meintjes, J. J. Calitz