The two-component afterglow of Swift GRB 050802

S. R. Oates, M. De Pasquale, M. J. Page, A. J. Blustin, S. Zane, K. McGowan, K. O. Mason, T. S. Poole, P. Schady, P. W.A. Roming, K. L. Page, A. Falcone, N. Gehrels

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Abstract

This paper investigates GRB 050802, one of the best examples of a Swift gamma-ray burst afterglow that shows a break in the X-ray light curve, while the optical counterpart decays as a single power law. This burst has an optically bright afterglow of 16.5 mag, detected throughout the 170-650 nm spectral range of the Ultraviolet and Optical Telescope (UVOT) onboard Swift. Observations began with the X-ray Telescope and UVOT telescopes 286 s after the initial trigger and continued for 1.2 × 106 s. The X-ray light curve consists of three power-law segments: a rise until 420 s, followed by a slow decay with α = 0.63 ± 0.03 until 5000 s, after which, the light curve decays faster with a slope of α3 = 1.59 ± 0.03. The optical light curve decays as a single power law with αO = 0.82 ± 0.03 throughout the observation. The X-ray data on their own are consistent with the break at 5000 s being due to the end of energy injection. Modelling the optical to X-ray spectral energy distribution, we find that the optical afterglow cannot be produced by the same component as the X-ray emission at late times, ruling out a single-component afterglow. We therefore considered two-component jet models and find that the X-ray and optical emission is best reproduced by a model in which both components are energy injected for the duration of the observed afterglow and the X-ray break at 5000 s is due to a jet break in the narrow component. This bright, well-observed burst is likely a guide for interpreting the surprising finding of Swift that bursts seldom display achromatic jet breaks.

Original languageEnglish (US)
Pages (from-to)270-280
Number of pages11
JournalMonthly Notices of the Royal Astronomical Society
Volume380
Issue number1
DOIs
StatePublished - Sep 1 2007

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afterglows
light curve
x rays
telescopes
bursts
power law
decay
ultraviolet telescopes
energy
spectral energy distribution
gamma ray bursts
light emission
actuators
injection
slopes
modeling

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Oates, S. R., De Pasquale, M., Page, M. J., Blustin, A. J., Zane, S., McGowan, K., ... Gehrels, N. (2007). The two-component afterglow of Swift GRB 050802. Monthly Notices of the Royal Astronomical Society, 380(1), 270-280. https://doi.org/10.1111/j.1365-2966.2007.12054.x
Oates, S. R. ; De Pasquale, M. ; Page, M. J. ; Blustin, A. J. ; Zane, S. ; McGowan, K. ; Mason, K. O. ; Poole, T. S. ; Schady, P. ; Roming, P. W.A. ; Page, K. L. ; Falcone, A. ; Gehrels, N. / The two-component afterglow of Swift GRB 050802. In: Monthly Notices of the Royal Astronomical Society. 2007 ; Vol. 380, No. 1. pp. 270-280.
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Oates, SR, De Pasquale, M, Page, MJ, Blustin, AJ, Zane, S, McGowan, K, Mason, KO, Poole, TS, Schady, P, Roming, PWA, Page, KL, Falcone, A & Gehrels, N 2007, 'The two-component afterglow of Swift GRB 050802', Monthly Notices of the Royal Astronomical Society, vol. 380, no. 1, pp. 270-280. https://doi.org/10.1111/j.1365-2966.2007.12054.x

The two-component afterglow of Swift GRB 050802. / Oates, S. R.; De Pasquale, M.; Page, M. J.; Blustin, A. J.; Zane, S.; McGowan, K.; Mason, K. O.; Poole, T. S.; Schady, P.; Roming, P. W.A.; Page, K. L.; Falcone, A.; Gehrels, N.

In: Monthly Notices of the Royal Astronomical Society, Vol. 380, No. 1, 01.09.2007, p. 270-280.

Research output: Contribution to journalArticle

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AU - De Pasquale, M.

AU - Page, M. J.

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AU - Zane, S.

AU - McGowan, K.

AU - Mason, K. O.

AU - Poole, T. S.

AU - Schady, P.

AU - Roming, P. W.A.

AU - Page, K. L.

AU - Falcone, A.

AU - Gehrels, N.

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N2 - This paper investigates GRB 050802, one of the best examples of a Swift gamma-ray burst afterglow that shows a break in the X-ray light curve, while the optical counterpart decays as a single power law. This burst has an optically bright afterglow of 16.5 mag, detected throughout the 170-650 nm spectral range of the Ultraviolet and Optical Telescope (UVOT) onboard Swift. Observations began with the X-ray Telescope and UVOT telescopes 286 s after the initial trigger and continued for 1.2 × 106 s. The X-ray light curve consists of three power-law segments: a rise until 420 s, followed by a slow decay with α = 0.63 ± 0.03 until 5000 s, after which, the light curve decays faster with a slope of α3 = 1.59 ± 0.03. The optical light curve decays as a single power law with αO = 0.82 ± 0.03 throughout the observation. The X-ray data on their own are consistent with the break at 5000 s being due to the end of energy injection. Modelling the optical to X-ray spectral energy distribution, we find that the optical afterglow cannot be produced by the same component as the X-ray emission at late times, ruling out a single-component afterglow. We therefore considered two-component jet models and find that the X-ray and optical emission is best reproduced by a model in which both components are energy injected for the duration of the observed afterglow and the X-ray break at 5000 s is due to a jet break in the narrow component. This bright, well-observed burst is likely a guide for interpreting the surprising finding of Swift that bursts seldom display achromatic jet breaks.

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Oates SR, De Pasquale M, Page MJ, Blustin AJ, Zane S, McGowan K et al. The two-component afterglow of Swift GRB 050802. Monthly Notices of the Royal Astronomical Society. 2007 Sep 1;380(1):270-280. https://doi.org/10.1111/j.1365-2966.2007.12054.x