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arXiv 2102.12588astro-ph.HE
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次级Cosmic-Ray核光谱硬化的起源

Origin of Spectral Hardening of Secondary Cosmic-Ray Nuclei

Norita Kawanaka, Shiu-Hang Lee

摘要:

讨论了在被星际介质(ISM)或星周介质(CSM)包围的超新星遗迹(SNRs)中,由碳、氮、氧等初级宇宙线核在激波加速后的散射所产生的次级宇宙线核(如锂、铍、硼)的加速和逃逸。我们考虑到CR粒子从SNR冲击中的能量依赖性逃逸,这是由SNR的γ射线观测所支持的,以计算初级和次级CR核逃逸到周围介质中的光谱。我们发现,如果SNR被具有风状密度分布的CSM包围(即,$n_{\rm CSM}\propto r^{-2}$),逃逸次级核的光谱比逃逸初级核的光谱硬,而如果SNR被均匀ISM包围,逃逸次级核的光谱总是比逃逸初级核的光谱软。利用这一结果,我们表明,如果有一个过去的超新星周围的一个密集的风一样的CSM($\sim 2.5\times 10^{-3}M_{\odot}~{\rm yr}^{-1}$)发生在$\sim 1.6\times 10^5~{\rm yr}$前在$\sim 1.6~{\rm kpc}$的距离,我们可以同时再现光谱硬化的初级和次级CR以上$\sim 200~{\rm GV}$,最近被AMS-02报道。

英文摘要:

We discuss the acceleration and escape of secondary cosmic-ray (CR) nuclei, such as lithium, beryllium and boron, produced by spallation of primary CR nuclei like carbon, nitrogen, and oxygen accelerated at the shock in supernova remnants (SNRs) surrounded by the interstellar medium (ISM) or a circumstellar medium (CSM). We take into account the energy-dependent escape of CR particles from the SNR shocks, which is supported by gamma-ray observations of SNRs, to calculate the spectra of primary and secondary CR nuclei running away into the ambient medium. We find that if the SNR is surrounded by a CSM with a wind-like density distribution (i.e., $n_{\rm CSM}\propto r^{-2}$), the spectra of the escaping secondary nuclei are harder than those of the escaping primary nuclei, while if the SNR is surrounded by a uniform ISM, the spectra of the escaping secondaries are always softer than those of the escaping primaries. Using this result, we show that if there was a past supernova surrounded by a dense wind-like CSM ($\sim 2.5\times 10^{-3}M_{\odot}~{\rm yr}^{-1}$) which happened $\sim 1.6\times 10^5~{\rm yr}$ ago at a distance of $\sim 1.6~{\rm kpc}$, we can simultaneously reproduce the spectral hardening of primary and secondary CRs above $\sim 200~{\rm GV}$ that have recently been reported by AMS-02.

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