GRB 021004 modelled by multiple energy injections

GRB021004 is one of the best sampled gamma-ray bursis (GRB) to date. although the nature of its light curve is still being debated. Here we present 107 new optical, near-infrared (NIR) and millimetre observations, ranging from 2 h to more than a year after the burst. Fitting the inultiband data to a model based on multiple energy injections suggests that at least 7 refreshed shocks took place during the evolution of the afterglow, implying a total energy release (collimated within an angle of 1:8) of ∼8 x 10 51 erg. Analysis of the late photometry reveals that the GRB021004 host is a low extinction (A V ∼ 0.1) starburst galaxy with M B ≃ -22.0.

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