Origin of Spectral Hardening of Secondary Cosmic-Ray Nuclei
Origin of Spectral Hardening of Secondary Cosmic-Ray Nuclei
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DOI：
10.3847/1538-4357/ac0a71
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发表时间：
2021-02
期刊：
影响因子：
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通讯作者：
N. Kawanaka;Shiu-Hang Lee
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文献类型：
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作者：
N. Kawanaka;Shiu-Hang Lee
我们讨论了在被星际介质（ISM）或星周介质（CSM）包围的超新星残余物（SNRs）中，由碳、氮和氧等初级宇宙射线（CR）核在激波下加速崩裂而产生的二次宇宙射线（CR）核，如锂、铍和硼的加速和逃逸。我们考虑了CR粒子从信噪比冲击中逃逸的能量依赖，这是由信噪比的伽马射线观测支持的，以计算逃逸到环境介质中的初级和次级CR核的光谱。我们发现，当信噪比被密度呈风状分布（即n CSM∝r−2）的CSM包围时，逃逸次级核的光谱比逃逸初级核的谱要硬，而当信噪比被均匀的CSM包围时，逃逸次级核的光谱总是比逃逸初级核的谱要软。利用这一结果，我们表明，如果过去有一颗超新星被密集的风状CSM （~ 2.5 × 10−3 M⊙yr−1）包围，这颗超新星发生在~ 1.6 × 105年前，距离~ 1.6 kpc，我们可以同时重现AMS-02最近报道的在~ 200 GV以上的初级和次级CRs的光谱硬化。
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 CSM ∝ 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 (∼2.5 × 10−3 M ⊙ yr−1), which happened ∼1.6 × 105 yr ago at a distance of ∼1.6 kpc, we can simultaneously reproduce the spectral hardening of primary and secondary CRs above ∼200 GV that have recently been reported by AMS-02.