RT Journal Article T1 GRB 021004 modelled by multiple energy injections A1 Ugarte Postigo, A. de A1 Castro Tirado, A. J. A1 Gorosabel, J. A1 Jóhannesson, G. A1 Björnsson, G. A1 Gudmundsson, E. H. A1 Bremer, M. A1 Pak, S. A1 Tanvir, N. A1 Castro Cerón, J. M. A1 Guzyi, S. A1 Jelínek, M. A1 Klose, S. A1 Pérez Ramírez, D. A1 Aceituno, J. A1 Campo Bagatín, A. A1 Covino, S. A1 Cardiel López, Nicolás AB 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. PB EDP Sciencies SN 0004-6361 YR 2005 FD 2005-12 LK https://hdl.handle.net/20.500.14352/51333 UL https://hdl.handle.net/20.500.14352/51333 LA eng NO © 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. NO INSU/CNRS (France) NO Spain’s Ministerio de Ciencia y Tecnología NO FPU grant from Spain’s Ministerio de Educación y Ciencia NO Icelandic Research Council NO Russian Foundation for Basic Research NO FEDER funds DS Docta Complutense RD 10 abr 2025