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Colour variations in the GRB 120327A afterglow

  • A. Melandri
  • , S. Covino
  • , E. Zaninoni
  • , S. Campana
  • , J. Bolmer
  • , B. E. Cobb
  • , J. Gorosabel
  • , J. W. Kim
  • , P. Kuin
  • , D. Kuroda
  • , D. Malesani
  • , C. G. Mundell
  • , F. Nappo
  • , B. Sbarufatti
  • , R. J. Smith
  • , I. A. Steele
  • , M. Topinka
  • , A. S. Trotter
  • , F. J. Virgili
  • , M. G. Bernardini
  • P. D'Avanzo, V. D'Elia, D. Fugazza, G. Ghirlanda, A. Gomboc, J. Greiner, C. Guidorzi, J. B. Haislip, H. Hanayama, L. Hanlon, M. Im, K. M. Ivarsen, J. Japelj, M. Jelínek, N. Kawai, S. Kobayashi, D. Kopac, A. P. Lacluyzé, A. Martin-Carrillo, D. Murphy, D. E. Reichart, R. Salvaterra, O. S. Salafia, G. Tagliaferri, S. D. Vergani

Research output: Contribution to journalArticlepeer-review

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.

Original languageEnglish (US)
Article numberA29
JournalAstronomy and Astrophysics
Volume607
DOIs
StatePublished - Nov 1 2017

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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