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arXiv 2006.02060astro-ph.HE
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短伽马射线暴的喷流结构和内禀光度函数

The jet structure and the intrinsic luminosity function of short gamma-ray bursts

Wei-Wei Tan, Yun-Wei Yu

摘要:

对GW 170817和GRB 170817 A的联合观测表明,短伽马射线暴(SGRB)可以起源于双星中子星合并。此外,一些SGRB可以检测到离轴,而SGRB射流是高度结构化的。然后,通过假设所有SGRB的喷流发射的普适角分布,我们再现了由{ \it Swift}和{ \it Fermi}探测到的宇宙学SGRB的通量和红移分布。对于自洽性,这种角分布同时受到GRB 170817 A的光度和事件率的约束。结果表明,SGRB的普遍喷流结构近似为双高斯分布。同时,喷流轴上发射的内禀光度函数(LF)可以简单地用一个低光度指数截止的幂律方程来描述。通常发现的相对高光度的破幂律表观LF可以自然地由本征LF与喷流发射的角分布的耦合引起,因为到SGRB的视角是任意分布的。

英文摘要:

The joint observation of GW170817 and GRB 170817A indicated that short gamma-ray bursts (SGRBs) can originate from binary neutron star mergers. Moreover, some SGRBs could be detected off-axis, while the SGRB jets are highly structured. Then, by assuming an universal angular distribution of the jet emission for all SGRBs, we re-produce the flux and redshift distributions of the cosmological SGRBs detected by {\it Swift} and {\it Fermi}. For self-consistency, this angular distribution is simultaneously constrained by the luminosity and event rate of GRB 170817A. As a result, it is found that the universal jet structure of SGRBs could approximately have a two-Gaussian profile. Meanwhile, the intrinsic luminosity function (LF) of the on-axis emission of the jets can be simply described by a single power law with a low-luminosity exponential cutoff. The usually discovered broken-power-law apparent LF for relatively high luminosities can naturally result from the coupling of the intrinsic LF with the angular distribution of the jet emission, as the viewing angles to the SGRBs are arbitrarily distributed.

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