  The rapid localization of GRB 021004 by the HETE-2 satellite allowed nearly
continuous monitoring of its early optical afterglow decay, as well as
high-quality optical spectra that determined a redshift of z=2.328 for its
host, an active starburst galaxy with strong Lyman-alpha emission and several
absorption lines. Spectral observations show multiple absorbers blueshifted by
up to 3,155 km/s relative to the host galaxy Lyman-alpha emission.We argue that
these correspond to a fragmented shell nebula, gradually enriched by a
Wolf-Rayet wind over the lifetime of a massive progenitor bubble. In this
scenario, the absorbers can be explained by circumstellar material that have
been radiatively accelerated by the GRB emission. Dynamical and photoionization
models are used to provide constraints on the radiative acceleration from the
early afterglow.
