LHAASO Constraints on New-Source Cosmic Rays:Abundance Scenarios and Injection Spectral Indices
Abstract
Recent LHAASO observations indicate that microquasars and massive star clusters contribute to Galactic cosmic rays, and likely also to the pre-knee spectral hardening. Their markedly different astrophysical environments, compared with supernova remnants (SNRs), may imprint distinct cosmic-ray abundances. We investigate the spectra and composition of new-source cosmic rays under two abundance scenarios: Case-1, the SNR-like composition with enhanced heavy nuclei, and Case-2, the surface abundances of microquasar companion stars. We constrain injection spectral indices using LHAASO proton, helium, and all-particle spectra, and use their data for model discrimination. Under the assumption of a unified heavy-element injection spectrum, Case-2 fits the data significantly better than Case-1, but at the cost of large, physically unmotivated differences between heavy-element and He injection indices. This suggests the need to either relax the unified heavy-element injection-index assumption or explore alternative abundance patterns. We predict that if the new-source composition follows Case-1, the individual elemental spectral indices before the knee should remain nearly consistent; if it follows Case-2, the Mg, Si, and Fe spectra will be significantly softer than those of He, C, and O. Future element-resolved energy-spectrum measurements by HERD and LHAASO will provide a decisive test of this discriminating feature.
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BibTeX
@misc{dong2026lhaaso,
title = {{LHAASO Constraints on New-Source Cosmic Rays:Abundance Scenarios and Injection Spectral Indices}},
author = {Xu-Lin Dong and Pei-Pei Zhang and Qi-Ling Chen and Shu-Wang Cui and Yi-Qing Guo},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.20477},
eprint = {2610.20477},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.20477},
}
RIS
TY - UNPB
TI - LHAASO Constraints on New-Source Cosmic Rays:Abundance Scenarios and Injection Spectral Indices
AU - Xu-Lin Dong
AU - Pei-Pei Zhang
AU - Qi-Ling Chen
AU - Shu-Wang Cui
AU - Yi-Qing Guo
PY - 2026
DA - 2026/10/23
PB - arXiv
DO - 10.48550/arxiv.2610.20477
UR - https://arxiv.org/abs/2610.20477
AB - Recent LHAASO observations indicate that microquasars and massive star clusters contribute to Galactic cosmic rays, and likely also to the pre-knee spectral hardening. Their markedly different astrophysical environments, compared with supernova remnants (SNRs), may imprint distinct cosmic-ray abundances. We investigate the spectra and composition of new-source cosmic rays under two abundance scenarios: Case-1, the SNR-like composition with enhanced heavy nuclei, and Case-2, the surface abundances of microquasar companion stars. We constrain injection spectral indices using LHAASO proton, helium, and all-particle spectra, and use their data for model discrimination. Under the assumption of a unified heavy-element injection spectrum, Case-2 fits the data significantly better than Case-1, but at the cost of large, physically unmotivated differences between heavy-element and He injection indices. This suggests the need to either relax the unified heavy-element injection-index assumption or explore alternative abundance patterns. We predict that if the new-source composition follows Case-1, the individual elemental spectral indices before the knee should remain nearly consistent; if it follows Case-2, the Mg, Si, and Fe spectra will be significantly softer than those of He, C, and O. Future element-resolved energy-spectrum measurements by HERD and LHAASO will provide a decisive test of this discriminating feature.
ER -