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Transition from fireball to Poynting-flux-dominated outflow in the three-episode GRB 160625B
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(2018) Transition from fireball to Poynting-flux-dominated outflow in the three-episode GRB 160625B. Nature Astronomy, 2 (1). pp. 69-75. doi:10.1038/s41550-017-0309-8 ISSN 2397-3366. An open access version can be found in:
Official URL: http://dx.doi.org/10.1038/s41550-017-0309-8
Abstract
The ejecta composition is an open question in gamma-ray burst (GRB) physics1. Some GRBs possess a quasi-thermal spectral component in the time-resolved spectral analysis2, suggesting a hot fireball origin. Others show a featureless non-thermal spectrum known as the Band function3,4,5, consistent with a synchrotron radiation origin5,6 and suggesting that the jet is Poynting-flux dominated at the central engine and probably in the emission region as well7,8. There are also bursts showing a sub-dominant thermal component and a dominant synchrotron component9, suggesting a probable hybrid jet composition10. Here, we report an extraordinarily bright GRB 160625B, simultaneously observed in gamma-ray and optical wavelengths, whose prompt emission consists of three isolated episodes separated by long quiescent intervals, with the durations of each sub-burst being approximately 0.8 s, 35 s and 212 s, respectively. Its high brightness (with isotropic peak luminosity Lp,iso ≈ 4 × 1053 erg s−1) allows us to conduct detailed time-resolved spectral analysis in each episode, from precursor to main burst and to extended emission. The spectral properties of the first two sub-bursts are distinctly different, allowing us to observe the transition from thermal to non-thermal radiation between well-separated emission episodes within a single GRB. Such a transition is a clear indication of the change of jet composition from a fireball to a Poynting-flux-dominated jet.
Item Type: | Journal Article | ||||||||
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Subjects: | Q Science > QC Physics | ||||||||
Divisions: | Faculty of Science, Engineering and Medicine > Science > Physics | ||||||||
Journal or Publication Title: | Nature Astronomy | ||||||||
Publisher: | Nature Publishing Group | ||||||||
ISSN: | 2397-3366 | ||||||||
Official Date: | January 2018 | ||||||||
Dates: |
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Volume: | 2 | ||||||||
Number: | 1 | ||||||||
Page Range: | pp. 69-75 | ||||||||
DOI: | 10.1038/s41550-017-0309-8 | ||||||||
Status: | Peer Reviewed | ||||||||
Publication Status: | Published | ||||||||
Access rights to Published version: | Restricted or Subscription Access | ||||||||
Related URLs: | |||||||||
Open Access Version: |
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