Photosphere–internal shock model of gamma-ray bursts: case studies of Fermi/LAT bursts
Photosphere–internal shock model of gamma-ray bursts: case studies of Fermi/LAT bursts
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DOI：
10.1111/j.1365-2966.2011.18807.x
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发表时间：
2010-02
影响因子：
4.8
通讯作者：
K. Toma;Xuefeng Wu;P. Mészáros
中科院分区：
文献类型：
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作者：
K. Toma;Xuefeng Wu;P. Mészáros
径向非均匀伽马射线暴（GRB）喷流释放出可变的光球辐射，并且可以在光球之上产生内部冲击。我们一般建立了grb的光球发射模型，包括内部激波中电子（和正电子）的康普顿上散射光球（UP）发射，并发现光球发射可能对应于传统（波段）成分小于或接近1 MeV， UP发射可能对应于Fermi/LAT观测到的一些grb大于或接近10 MeV的高能发射。在某些情况下，这两个分量可以在频谱中彼此分离，或者在其他情况下可以模拟平滑的宽带频谱。我们将我们的公式应用于已经得到充分研究的长、短LAT伽玛暴，GRB 080916C， GRB 090902B和GRB 090510，并找到了合理的参数来拟合时间盒光谱，尽管需要对几个参数进行微调。观测到的高能发射相对于MeV发射的延迟与变率时间相比较大，不太可能是由于非演化射流的简单运动效应。这些延迟可能归因于喷流物理参数的时间演化，因此延迟时间尺度可以为研究GRB喷流本身及其前身的结构提供潜在的工具。从费米数据推断出的长、短伽马射线暴延迟时间尺度的差异可能是由于长、短伽马射线暴的祖元不同所致。讨论了该模型的其他一些性质和结果，包括瞬态光学、软x射线和不同高能成分以及波段成分之间的时间相关性。
Radially inhomogeneous gamma-ray burst (GRB) jets release variable photospheric emission and can have internal shocks occurring above the photosphere. We generically formulate a photospheric emission model of GRBs including Compton up-scattered photospheric (UP) emission off the electrons (and positrons) in the internal shocks, and find that the photospheric emission may correspond to the traditional (band) component at less than or similar to 1 MeV and the UP emission to the high-energy emission observed by Fermi/LAT for some GRBs at greater than or similar to 10 MeV. The two components can be separate from each other in the spectrum in some cases or can mimic a smooth broad-band spectrum in other cases. We apply our formulation to the well-studied long and short LAT GRBs, GRB 080916C, GRB 090902B and GRB 090510, and typically find reasonable parameters for fitting the time-binned spectra, although fine-tuning of several parameters is required. The observed delays of the high-energy emission with respect to the MeV emission which are large compared to the variability times are unlikely to be due to simple kinematic effects of a non-evolving jet. These delays may instead be attributed to the temporal evolution of the physical parameters of the jet, and thus the delay time-scales could provide a potential tool for investigating the structures of GRB jets themselves and their progenitors. The difference of the delay time-scales of long and short GRBs inferred from the Fermi data might be due to the differences in the progenitors of long and short GRBs. Some other properties and consequences of this model are discussed, including temporal correlations among the prompt optical, the soft X-ray and the distinct high-energy component as well as the band component.