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Colour variations in the GRB 120327A afterglow

Abstract : Aims. We present a comprehensive temporal and spectral analysis of the long Swift GRB 120327A afterglow data to investigate possible causes of the observed early-time colour variations.Methods. We collected data from various instruments and telescopes in X-ray, ultraviolet, optical, and near-infrared bands, and determined the shapes of the afterglow early-time light curves. We studied the overall temporal behaviour and the spectral energy distributions from early to late times.Results. The ultraviolet, optical, and near-infrared light curves can be modelled with a single power-law component between 200 and 2 × 104 s after the burst event. The X-ray light curve shows a canonical steep-shallow-steep behaviour that is typical of long gamma-ray bursts. At early times a colour variation is observed in the ultraviolet/optical bands, while at very late times a hint of a re-brightening is visible. The observed early-time colour change can be explained as a variation in the intrinsic optical spectral index, rather than an evolution of the optical extinction.Key words: gamma-ray burst: individual: GRB 120327A / dust, extinction⋆ Table 2 is only available at the CDS via anonymous ftp to ( or via⋆⋆ Deceased.
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Submitted on : Friday, August 5, 2022 - 8:33:06 AM
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A. Melandri, S. Covino, E. Zaninoni, S. Campana, J. Bolmer, et al.. Colour variations in the GRB 120327A afterglow. Astron.Astrophys., 2017, 607, pp.A29. ⟨10.1051/0004-6361/201731759⟩. ⟨hal-01645283⟩



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