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| Format: | Preprint |
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2026
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| Online-Zugang: | https://arxiv.org/abs/2603.26326 |
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| _version_ | 1866914426628603904 |
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| author | Li, Bo-Tao Wang, Wei Li, Zhuo |
| author_facet | Li, Bo-Tao Wang, Wei Li, Zhuo |
| contents | Recently, the GeV--sub-PeV spectrum of supernova remnant (SNR) Cassiopeia A (Cas A), one of the youngest and most well-studied SNRs in our Galaxy, has been updated by observations of Fermi-LAT and LHAASO. We revisit Cas A with our previous shell-plus-jet asymmetric model and investigate its particle acceleration ability. The broadband fitting results suggest that the double-peaked gamma-ray spectrum can be well attributed to proton-proton (PP) collisions and inverse Compton scattering within the SNR shell, while the synchrotron emission from a jet component with velocity of $\sim0.1c$ can account for the hard X-ray emission up to 220 keV. Furthermore, the PP collisions in the jet can produce a sub-PeV emission, but constrained by the LHAASO-KM2A limit to a flux below $\sim 1\times10^{-14}\rm erg/(cm^2s)$ at 100 TeV. The energy of accelerated protons in the jet of Cas A could be up to $5\times10^{47}$ erg, which, assuming that the PeV cosmic ray distribution is clumpy in the Galaxy with the clump size comparable to the thickness of the Galactic plane, derives a proton flux consistent with the observed one at 1 PeV, implying that the Cas A-like SNRs can still be PeVatrons in the Galaxy. It is encouraging for LHAASO and future telescopes to detect or constrain Cas A spectrum above 100-TeV more precisely. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2603_26326 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Particle Acceleration in Cassiopeia A Revealed by Broadband High-Energy Spectrum Li, Bo-Tao Wang, Wei Li, Zhuo High Energy Astrophysical Phenomena Recently, the GeV--sub-PeV spectrum of supernova remnant (SNR) Cassiopeia A (Cas A), one of the youngest and most well-studied SNRs in our Galaxy, has been updated by observations of Fermi-LAT and LHAASO. We revisit Cas A with our previous shell-plus-jet asymmetric model and investigate its particle acceleration ability. The broadband fitting results suggest that the double-peaked gamma-ray spectrum can be well attributed to proton-proton (PP) collisions and inverse Compton scattering within the SNR shell, while the synchrotron emission from a jet component with velocity of $\sim0.1c$ can account for the hard X-ray emission up to 220 keV. Furthermore, the PP collisions in the jet can produce a sub-PeV emission, but constrained by the LHAASO-KM2A limit to a flux below $\sim 1\times10^{-14}\rm erg/(cm^2s)$ at 100 TeV. The energy of accelerated protons in the jet of Cas A could be up to $5\times10^{47}$ erg, which, assuming that the PeV cosmic ray distribution is clumpy in the Galaxy with the clump size comparable to the thickness of the Galactic plane, derives a proton flux consistent with the observed one at 1 PeV, implying that the Cas A-like SNRs can still be PeVatrons in the Galaxy. It is encouraging for LHAASO and future telescopes to detect or constrain Cas A spectrum above 100-TeV more precisely. |
| title | Particle Acceleration in Cassiopeia A Revealed by Broadband High-Energy Spectrum |
| topic | High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2603.26326 |