Ugarte Postigo, A. deCastro Tirado, A. J.Gorosabel, J.Jóhannesson, G.Björnsson, G.Gudmundsson, E. H.Bremer, M.Pak, S.Tanvir, N.Castro Cerón, J. M.Guzyi, S.Jelínek, M.Klose, S.Pérez Ramírez, D.Aceituno, J.Campo Bagatín, A.Covino, S.Cardiel López, Nicolás2023-06-202023-06-202005-120004-636110.1051/0004-6361;20052898https://hdl.handle.net/20.500.14352/51333© ESO 2005. Artículo firmado por 46 autores. We acknowledge the generous allocation of observing time by different Time Allocation Committees at several observatories spread world-wide. Partly based on observations carried out with the IRAM Plateau de Bure Interferometer. IRAM is supported by INSU/CNRS (France), MPG (Germany) and ING (Spain). This research has been partially supported by the Spain’s Ministerio de Ciencia y Tecnología under programmes ESP2002-04124-C03-01 and AYA2004-01515 (including FEDER funds). A. de Ugarte Postigo acknowledges support from a FPU grant from Spain’s Ministerio de Educación y Ciencia. G. Jóhannesson, G. Björnsson and E. H. Gudmundsson acknowledge support from a special grant from the Icelandic Research Council. V. V. Sokolov and T. A. Fatkhullin were supported by Russian Foundation for Basic Research, grant No. 01- 02-17106. We acknowledge our anonymous referee for constructive comments.GRB 021004 is one of the best sampled gamma-ray bursts (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 multiband 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.degrees 8) of similar to 8 x 10(51) erg. Analysis of the late photometry reveals that the GRB 021004 host is a low extinction (A(V) similar to 0.1) starburst galaxy with M-B similar or equal to -22.0.engjournal articlehttp://dx.doi.org/10.1051/0004-6361:20052898http://www.aanda.org/open access52Gamma-ray burstLight curvesOptical afterglowGRBVariabilityGRB-000926ProgenitorEmissionDynamicsGalaxiesAstrofísicaAstronomía (Física)Física atmosférica2501 Ciencias de la Atmósfera