Colour variations in the GRB 120327A afterglow
Journal
Date Issued
2017
Author(s)
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Zaninoni, E.
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Bolmer, J.
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Cobb, B. E.
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Gorosabel, J.
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Kim, J. -W.
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Kuin, P.
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Kuroda, D.
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Malesani, D.
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Mundell, C. G.
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Nappo, F.
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Smith, R. J.
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Steele, I. A.
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Trotter, A. S.
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Virgili, F. J.
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D'Elia, V.
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Gomboc, A.
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Greiner, J.
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Guidorzi, C.
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Haislip, J. B.
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Hanayama, H.
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Hanlon, L.
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Im, M.
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Ivarsen, K. M.
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Japelj, J.
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Jelínek, M.
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Kawai, N.
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Kobayashi, S.
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Kopac, D.
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LaCluyzé, A. P.
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Martin-Carrillo, A.
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Murphy, D.
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Reichart, D. E.
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Vergani, S. D.
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. Table 2 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/607/A29
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. Table 2 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/607/A29
Volume
607
Start page
A29
Issn Identifier
0004-6361
Ads BibCode
2017A&A...607A..29M
Rights
open.access
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