"Double-tracking" Characteristics of the Spectral Evolution of GRB 131231A: Synchrotron Origin?

"Double-tracking" Characteristics of the Spectral Evolution of GRB 131231A: Synchrotron Origin?

The characteristics of the spectral evolution of the prompt emission of gamma-ray bursts (GRBs), which are closely related to the radiation mechanism (synchrotron or photosphere), are still an unsolved subject. Here, by performing the detailed time-resolved spectral fitting of GRB 131231A, which has...

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Bibliographic Details
Published in:The Astrophysical journal 2019-10, Vol.884 (2), p.109
Main Authors: Li, Liang, Geng, Jin-Jun, Meng, Yan-Zhi, Wu, Xue-Feng, Huang, Yong-Feng, Wang, Yu, Moradi, Rahim, Uhm, Z. Lucas, Zhang, Bing
Format: Article
Language:eng
Subjects:
Emission
Emissions
Emitters
Energy flux
Evolution
Gamma ray bursts
Gamma rays
gamma-ray burst: general
Photosphere
Radiation
radiation mechanisms: non-thermal
Spectra
Tracking
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Summary:The characteristics of the spectral evolution of the prompt emission of gamma-ray bursts (GRBs), which are closely related to the radiation mechanism (synchrotron or photosphere), are still an unsolved subject. Here, by performing the detailed time-resolved spectral fitting of GRB 131231A, which has a very bright and well-defined single pulse, some interesting spectral evolution features have been found. (i) Both the low-energy spectral index and the peak energy Ep exhibit the "flux-tracking" pattern ("double-tracking" characteristics). (ii) The parameter relations, i.e., F (the energy flux)- , F-Ep, and Ep- , along with the analogous Yonetoku Ep-Lγ,iso relation for the different time-resolved spectra, show strong monotonous (positive) correlations, both in the rising and the decaying phases. (iii) The values of do not exceed the synchrotron limit ( = −2/3) in all slices across the pulse, favoring the synchrotron origin. We argue that the one-zone synchrotron emission model with the emitter streaming away at a large distance from the central engine can explain all of these special spectral evolution characteristics.
ISSN:0004-637X
1538-4357