arXivDaily arXiv每日学术速递 周一至周五更新
arXiv周末暂无论文更新,休息一下吧,周末愉快~~
arXiv 2210.07090astro-ph.HE
收藏

UHECR源有限寿命的影响

Impact of the finite life-time of UHECR sources

Björn Eichmann, Michael Kachelrieß

摘要:

高能宇宙射线(UHECR)的观测数据,特别是它们的质量组成,显示出强烈的迹象,极硬光谱的个别质量群的CR核在地球上。在这项工作中,我们表明,这样的硬谱可以是有限的寿命的UHECR源的结果,如果少数个别源占主导地位的UHECR通量在最高的能量。在这种情况下,在湍流河外磁场以及从源环境的扩散或平流逃逸偏转引起的时间延迟可以抑制低能量CR,导致所观察到的光谱变陡。考虑到无线电星系的主要来源的UHECRs,我们讨论的必要条件,几个单独的源占主导地位的总贡献,从大部分的源,在过去一直活跃。我们提供了两个证明的原则方案表明,对于一个湍流河外磁场的强度$B$和相干长度$l_{\rm coh}$,在距离$d_{\rm src}$源的寿命应满足${t_{\rm act} \sim \left( B/1\,\text{nG} \right)^2\,\left( d_{\rm src}/10\,\text{Mpc} \right)^2\,\left( l_{\rm coh}/1\,\text{Mpc} \right)\,\text{Myr}}$,以获得必要的硬化的CR谱在地球上。

英文摘要:

The observational data on ultrahigh energy cosmic rays (UHECR), in particular their mass composition, show strong indications for extremely hard spectra of individual mass groups of CR nuclei at Earth. In this work, we show that such hard spectra can be the result of the finite life-time of UHECR sources, if a few individual sources dominate the UHECR flux at the highest energies. In this case, time delays induced by deflections in the turbulent extragalactic magnetic field as well as from the diffusive or advective escape from the source environment can suppress low-energy CRs, leading to a steepening of the observed spectrum. Considering radio galaxies as the main source of UHECRs, we discuss the necessary conditions that few individual sources dominate over the total contribution from the bulk of sources that have been active in the past. We provide two proof-of-principle scenarios showing that for a turbulent extragalactic magnetic field with a strength $B$ and a coherence length $l_{\rm coh}$, the life-time of a source at a distance $d_{\rm src}$ should satisfy ${t_{\rm act} \sim \left( B/1\,\text{nG} \right)^2\,\left( d_{\rm src}/10\,\text{Mpc} \right)^2\,\left( l_{\rm coh}/1\,\text{Mpc} \right)\,\text{Myr}}$ to obtain the necessary hardening of the CR spectrum at Earth.

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。

↑