The circumburst environment of a FRED GRB

Study of the prompt emission and X-ray/optical afterglow of GRB 051111

C. Guidorzi, A. Gomboc, S. Kobayashi, C. G. Mundell, E. Rol, M. F. Bode, D. Carter, V. La Parola, A. Melandri, A. Monfardini, C. J. Mottram, P. T. O'Brien, K. L. Page, T. Sakamoto, R. J. Smith, I. A. Steele, N. R. Tanvir

Research output: Contribution to journalArticle

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Abstract

Aims. We report a multi-wavelength analysis of the prompt emission and early afterglow of GRB 051111 and discuss its properties in the context of current fireball models. Methods. The detection of GRB 051111 by the Burst Alert Telescope on-board Swift triggered early BVRi' observations with the 2-m robotic Faulkes Telescope North in Hawaii, as well as X-ray observations with the Swift X-Ray Telescope. Results. The prompt γ-ray emission shows a classical FRED profile. The optical afterglow light curves are fitted with a broken power law, with α1 = 0.35 to α2 = 1.35 and a break time around 12 min after the GRB. Although contemporaneous X-ray observations were not taken, a power law connection between the γ-ray tail of the FRED temporal profile and the late XRT flux decay is feasible. Alternatively, if the X-ray afterglow tracks the optical decay, this would represent one of the first GRBs for which the canonical steep-shallow-normal decay typical of early X-ray afterglows has been monitored optically. We present a detailed analysis of the intrinsic extinction, elemental abundances and spectral energy distribution. From the absorption measured in the low X-ray band we find possible evidence for an overabundance of some α elements such as oxygen, [O/Zn] = 0.7 ± 0.3, or, alternatively, for a significant presence of molecular gas. The IR-to-X-ray Spectral Energy Distribution measured at 80 min after the burst is consistent with the cooling break lying between the optical and X-ray bands. Extensive modelling of the intrinsic extinction suggests dust with big grains or grey extinction profiles. The early optical break is due either to an energy injection episode or, less probably, to a stratified wind environment for the circumburst medium.

Original languageEnglish
Pages (from-to)539-550
Number of pages12
JournalAstronomy and Astrophysics
Volume463
Issue number2
DOIs
Publication statusPublished - 4 Feb 2007

Fingerprint

afterglows
x rays
extinction
telescopes
spectral energy distribution
bursts
power law
decay
profiles
gamma rays
energy
fireballs
robotics
molecular gases
light curve
dust
injection
cooling
wavelength
oxygen

Keywords

  • Dust, extinction
  • Gamma rays: bursts
  • Radiation mechanisms: non-thermal
  • X-rays: individuals: GRB 051111

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

The circumburst environment of a FRED GRB : Study of the prompt emission and X-ray/optical afterglow of GRB 051111. / Guidorzi, C.; Gomboc, A.; Kobayashi, S.; Mundell, C. G.; Rol, E.; Bode, M. F.; Carter, D.; La Parola, V.; Melandri, A.; Monfardini, A.; Mottram, C. J.; O'Brien, P. T.; Page, K. L.; Sakamoto, T.; Smith, R. J.; Steele, I. A.; Tanvir, N. R.

In: Astronomy and Astrophysics, Vol. 463, No. 2, 04.02.2007, p. 539-550.

Research output: Contribution to journalArticle

Guidorzi, C, Gomboc, A, Kobayashi, S, Mundell, CG, Rol, E, Bode, MF, Carter, D, La Parola, V, Melandri, A, Monfardini, A, Mottram, CJ, O'Brien, PT, Page, KL, Sakamoto, T, Smith, RJ, Steele, IA & Tanvir, NR 2007, 'The circumburst environment of a FRED GRB: Study of the prompt emission and X-ray/optical afterglow of GRB 051111', Astronomy and Astrophysics, vol. 463, no. 2, pp. 539-550. https://doi.org/10.1051/0004-6361:20065974
Guidorzi, C. ; Gomboc, A. ; Kobayashi, S. ; Mundell, C. G. ; Rol, E. ; Bode, M. F. ; Carter, D. ; La Parola, V. ; Melandri, A. ; Monfardini, A. ; Mottram, C. J. ; O'Brien, P. T. ; Page, K. L. ; Sakamoto, T. ; Smith, R. J. ; Steele, I. A. ; Tanvir, N. R. / The circumburst environment of a FRED GRB : Study of the prompt emission and X-ray/optical afterglow of GRB 051111. In: Astronomy and Astrophysics. 2007 ; Vol. 463, No. 2. pp. 539-550.
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