MELANDRI, AndreaAndreaMELANDRICOVINO, StefanoStefanoCOVINOZaninoni, E.E.ZaninoniCAMPANA, SergioSergioCAMPANABolmer, J.J.BolmerCobb, B. E.B. E.CobbGorosabel, J.J.GorosabelKim, J. -W.J. -W.KimKuin, P.P.KuinKuroda, D.D.KurodaMalesani, D.D.MalesaniMundell, C. G.C. G.MundellNappo, F.F.NappoSBARUFATTI, BorisBorisSBARUFATTISmith, R. J.R. J.SmithSteele, I. A.I. A.SteeleTopinka, M.M.TopinkaTrotter, A. S.A. S.TrotterVirgili, F. J.F. J.VirgiliBERNARDINI, Maria GraziaMaria GraziaBERNARDINID'AVANZO, PaoloPaoloD'AVANZOD'Elia, V.V.D'EliaFUGAZZA, Dino PierluigiDino PierluigiFUGAZZAGHIRLANDA, GiancarloGiancarloGHIRLANDAGomboc, A.A.GombocGreiner, J.J.GreinerGuidorzi, C.C.GuidorziHaislip, J. B.J. B.HaislipHanayama, H.H.HanayamaHanlon, L.L.HanlonIm, M.M.ImIvarsen, K. M.K. M.IvarsenJapelj, J.J.JapeljJelínek, M.M.JelínekKawai, N.N.KawaiKobayashi, S.S.KobayashiKopac, D.D.KopacLaCluyzé, A. P.A. P.LaCluyzéMartin-Carrillo, A.A.Martin-CarrilloMurphy, D.D.MurphyReichart, D. E.D. E.ReichartSALVATERRA, RubenRubenSALVATERRASalafia, Om SharanOm SharanSalafiaTAGLIAFERRI, GianpieroGianpieroTAGLIAFERRIVergani, S. D.S. D.Vergani2020-09-162020-09-1620170004-6361http://hdl.handle.net/20.500.12386/27389Aims: 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. <BR /> Results: The ultraviolet, optical, and near-infrared light curves can be modelled with a single power-law component between 200 and 2 × 10<SUP>4</SUP> 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. Table 2 is only available at the CDS via anonymous ftp to <A href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A> (<A href="http://130.79.128.5">http://130.79.128.5</A>) or via <A href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/607/A29">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/607/A29STAMPAenArticle10.1051/0004-6361/2017317592-s2.0-85032641680000414181400011https://www.aanda.org/articles/aa/abs/2017/11/aa31759-17/aa31759-17.html2017A&A...607A..29MFIS/05 - ASTRONOMIA E ASTROFISICA