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arXiv 1405.2091astro-ph.HE
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GRB模型中PeV中微子光谱截止的意义

Implications of a PeV neutrino spectral cutoff in GRB models

Maria Petropoulou, Dimitrios Giannios, Stavros Dimitrakoudis

摘要:

最近河外PeV中微子的发现为宇宙射线加速器的探索打开了一扇新的窗口。观测到的PeV中微子通量接近Waxman-Bahcall上限,这意味着伽马射线暴(GRB)可能是超高能宇宙射线(UHECR)的来源。从GRB-UHECR联系的假设出发,我们用解析估计和数值模拟表明,观测到的中微子可以起源于喷注,这是由于中微子与高能离子相互作用的结果,其含义是:中微子谱在能量$\le 10$ PeV处有一个截止,引起GRB发射和宇宙线加速的耗散发生在离中心引擎$r_{\rm diss} \approx 3 \times 10^{11}-3 \times 10^{13} \ {\rm cm}$的距离处;耗散区的汤姆逊光学深度为$τ_{\rm T} \sim 1$ ;喷流在耗散区以坡印廷通量的形式携带其能量的相当大的一部分,并具有洛伦兹因子$Γ\simeq 100-500$。没有探测到与伽玛暴同时发生的$\sim$ PeV中微子,这表明伽玛暴要么是较差的宇宙加速器,要么是在喷流中较小的光学深度处发生耗散。

英文摘要:

The recent discovery of extragalactic PeV neutrinos opens a new window to the exploration of cosmic-ray accelerators. The observed PeV neutrino flux is close to the Waxman-Bahcall upper bound implying that gamma-ray bursts (GRBs) may be the source of ultra-high energy cosmic rays (UHECRs). Starting with the assumption of the GRB-UHECR connection, we show using both analytical estimates and numerical simulations that the observed neutrinos can originate at the jet as a result of photopion interactions with the following implications: the neutrino spectra are predicted to have a cutoff at energy $\le 10$ PeV; the dissipation responsible for the GRB emission and cosmic-ray acceleration takes place at distances $r_{\rm diss} \approx 3 \times 10^{11}-3 \times 10^{13} \ {\rm cm}$ from the central engine; the Thomson optical depth at the dissipation region is $τ_{\rm T} \sim 1$; the jet carries a substantial fraction of its energy in the form of Poynting flux at the dissipation region, and has a Lorentz factor $Γ\simeq 100-500$. The non-detection of $\sim$PeV neutrinos coincident with GRBs will indicate that GRBs are either poor cosmic accelerators or the dissipation takes place at small optical depths in the jet.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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