  High resolution spectroscopy of GRB 021004 revealed a wealth of absorption
lines from several intermediate ionization species. The velocity structure of
the absorber is complex and material with velocity up to >3000 km/s is
observed. Since only the blueshifted component is observed, the absorber is
very likely to be material closely surrounding the gamma-ray burst. We use a
time-dependent photoionization code to track the abundance of the ions over
time. Thanks to the presence of absorption from intermediate ionization states
at long times, we can estimate the location and mass of the components of the
absorber. We interpret those constraints within the hypernova scenario showing
that the mass loss rate of the progenitor must have been ~10^{-4} solar masses
per year, suggestive of a very massive star. In addition, the wind termination
shock must lie at a distance of at least 100 pc, implying a low density
environment. The velocity structure of the absorber also requires clumping of
the wind at those large distances.
