Transition From Fireball To Poynting-flux-dominated Outflow In The Three-episode Grb 160625b

Authors

B B. Zhang, Nanjing UniversityFollow
B Zhang, University of Nevada, Las VegasFollow
A J. Castro-Tirado, Universidad de MálagaFollow
Z G. Dai, Nanjing UniversityFollow
P HT Tam, Sun Yat-Sen University
X Y. Wang, Nanjing UniversityFollow
Y D. Hu, Universidad de Granada
S Karpov, Kazan Federal University
A Pozanenko, Institute of the Russian Academy of SciencesFollow
F W. Zhang, Guilin University of Technology
E Mazæva, Institute of the Russian Academy of Sciences
P Minæv, Institute of the Russian Academy of Sciences
A Volnova, Institute of the Russian Academy of Sciences
S Oates, University of WarwickFollow
H Gao, Beijing Normal UniversityFollow
X F. Wu, University of Science and Technology of ChinaFollow
L Shao, Hebei Normal University
Q W. Tang, Nanchang UniversityFollow
G Beskin, Kazan Federal University
A Biryukov, Kazan Federal University
S Bondar, Research and Production Corporation
E Ivanov, Research and Production Corporation
E Katkova, Research and Production Corporation
N Orekhova, Research and Production Corporation
A Perkov, Research and Production Corporation
V Sasyuk, Kazan Federal University
L Mankiewicz, Center for Theoretical Physics PAS

Document Type

Article

Publication Date

1-1-2018

Publication Title

Nature Astronomy

Publisher

Nature Publishing Group

Volume

2

Issue

1

First page number:

69

Last page number:

75

Abstract

The ejecta composition is an open question in gamma-ray burst (GRB) physics 1 . Some GRBs possess a quasi-thermal spectral component in the time-resolved spectral analysis 2, suggesting a hot fireball origin. Others show a featureless non-thermal spectrum known as the Band function 3-5, consistent with a synchrotron radiation origin 5,6 and suggesting that the jet is Poynting-flux dominated at the central engine and probably in the emission region as well 7,8 . There are also bursts showing a sub-dominant thermal component and a dominant synchrotron component 9, suggesting a probable hybrid jet composition 10 . 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 L p,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. © 2017 The Author(s).

Language

English

Repository Citation

Zhang, B. B., Zhang, B., Castro-Tirado, A. J., Dai, Z. G., Tam, P. H., Wang, X. Y., Hu, Y. D., Karpov, S., Pozanenko, A., Zhang, F. W., Mazæva, E., Minæv, P., Volnova, A., Oates, S., Gao, H., Wu, X. F., Shao, L., Tang, Q. W., Beskin, G., Biryukov, A., Bondar, S., Ivanov, E., Katkova, E., Orekhova, N., Perkov, A., Sasyuk, V., Mankiewicz, L. (2018). Transition From Fireball To Poynting-flux-dominated Outflow In The Three-episode Grb 160625b. Nature Astronomy, 2(1), 69-75. Nature Publishing Group.
http://dx.doi.org/10.1038/s41550-017-0309-8