1. Colour variations in the GRB 120327A afterglow
- Author
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Nobuyuki Kawai, Stefano Covino, A. S. Trotter, Om Sharan Salafia, Jochen Greiner, Lorraine Hanlon, D. B. Malesani, F. Nappo, J. Japelj, Aaron P. LaCluyze, M. G. Bernardini, Robert J. Smith, Paul Kuin, Sergio Campana, K. M. Ivarsen, Giancarlo Ghirlanda, Daisuke Kuroda, Gianpiero Tagliaferri, P. D'Avanzo, Ruben Salvaterra, B. E. Cobb, Javier Gorosabel, F. J. Virgili, Valerio D'Elia, Dino Fugazza, H. Hanayama, J. Bolmer, C. Guidorzi, Shiho Kobayashi, Josh Haislip, M. Topinka, A. Gomboc, Martin Jelínek, Iain A. Steele, Antonio Martin-Carrillo, Carole Mundell, Jae Woo Kim, B. Sbarufatti, Drejc Kopač, Daniel E. Reichart, A. Melandri, E. Zaninoni, S. D. Vergani, Myungshin Im, David Murphy, European Commission, Slovenian Research Agency, National Research Foundation of Korea, Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (Brasil), Laboratoire Univers et Particules de Montpellier (LUPM), Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), Université de Montpellier (UM)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Montpellier 2 - Sciences et Techniques (UM2), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Univers et Particules de Montpellier ( LUPM ), Centre National de la Recherche Scientifique ( CNRS ) -Institut National de Physique Nucléaire et de Physique des Particules du CNRS ( IN2P3 ) -Université Montpellier 2 - Sciences et Techniques ( UM2 ) -Université de Montpellier ( UM ), Galaxies, Etoiles, Physique, Instrumentation ( GEPI ), and Institut national des sciences de l'Univers ( INSU - CNRS ) -Observatoire de Paris-Université Paris Diderot - Paris 7 ( UPD7 ) -Centre National de la Recherche Scientifique ( CNRS )
- Subjects
Cosmology and Nongalactic Astrophysics (astro-ph.CO) ,[ PHYS.ASTR ] Physics [physics]/Astrophysics [astro-ph] ,Astrophysics::High Energy Astrophysical Phenomena ,gamma-ray burst: individual: GRB 120327A, dust, extinction ,FOS: Physical sciences ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,01 natural sciences ,NO ,0103 physical sciences ,Spectral analysis ,individual: GRB 120327A [Gamma-ray burst] ,010303 astronomy & astrophysics ,QC ,Dust, extinction ,QB ,Physics ,High Energy Astrophysical Phenomena (astro-ph.HE) ,Spectral index ,010308 nuclear & particles physics ,extinction ,Spectral density ,Astronomy and Astrophysics ,Light curve ,gamma-ray burst: individual: GRB 120327A ,Afterglow ,Space and Planetary Science ,dust ,Astrophysics - High Energy Astrophysical Phenomena ,Gamma-ray burst ,[PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph] ,Event (particle physics) ,Astrophysics - Cosmology and Nongalactic Astrophysics - 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 × 10 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.© 2017 ESO., A.M., S.Co., S.Ca., B.S., P.D.A., and G.T. acknowledge support from the ASI grant I/004/11/3. E.Z. acknowledges the support by the International Cooperation Program CAPES-ICRANet financed by CAPES Brazilian Federal Agency for Support and Evaluation of Graduate Education within the Ministry of Education of Brazil. D.M. acknowledges support from the Instrument center for Danish Astrophysics (IDA). C.G.M. acknowledges support from the Royal Society, the Wolfson Foundation, and the Science and Technology Facilities Council. L.H. acknowledges support from SFI (07-RFP-PHYF295, 11/RFP.1/AST/3188) and the EU-FP7/GLORIA (grant No. 283783). M.I. and J.W.K. acknowledge the support from the National Research Foundation of Korea grant Nos. 2017R1A3A3001362 and 2016R1D1A1B03934815. D.K. acknowledges the financial support from the Slovenian Research Agency (P1-0188). This work has been supported by ASI grant I/004/11/0 and by PRIN-MIUR 2009 grants.
- Published
- 2017
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