🔭 astrophysics

Ultra-high-energy $\gamma$ -ray imprints from PeV particles accelerated by supernova remnants

Using observations from LHAASO, this paper provides evidence that two middle-aged supernova remnants (G150.3+4.5 and $\gamma$ -Cygni) accelerate hadronic cosmic rays up to PeV energies, which then produce ultra-high-energy $\gamma$ -ray emission through collisions with nearby molecular clouds.

Original authors: Zhen Cao (The LHAASO Collaboration), F. Aharonian (The LHAASO Collaboration), Y. X. Bai (The LHAASO Collaboration), Y. W. Bao (The LHAASO Collaboration), D. Bastieri (The LHAASO Collaboration), X. J. Zhen Cao (The LHAASO Collaboration), F. Aharonian (The LHAASO Collaboration), Y. X. Bai (The LHAASO Collaboration), Y. W. Bao (The LHAASO Collaboration), D. Bastieri (The LHAASO Collaboration), X. J. Bi (The LHAASO Collaboration), Y. J. Bi (The LHAASO Collaboration), W. Bian (The LHAASO Collaboration), J. Blunier (The LHAASO Collaboration), A. V. Bukevich (The LHAASO Collaboration), C. M. Cai (The LHAASO Collaboration), Y. Y. Cai (The LHAASO Collaboration), W. Y. Cao (The LHAASO Collaboration), Zhe Cao (The LHAASO Collaboration), J. Chang (The LHAASO Collaboration), J. F. Chang (The LHAASO Collaboration), E. S. Chen (The LHAASO Collaboration), G. H. Chen (The LHAASO Collaboration), H. K. Chen (The LHAASO Collaboration), L. F. Chen (The LHAASO Collaboration), Liang Chen (The LHAASO Collaboration), Long Chen (The LHAASO Collaboration), M. J. Chen (The LHAASO Collaboration), M. L. Chen (The LHAASO Collaboration), Q. H. Chen (The LHAASO Collaboration), S. Chen (The LHAASO Collaboration), S. H. Chen (The LHAASO Collaboration), S. Z. Chen (The LHAASO Collaboration), T. L. Chen (The LHAASO Collaboration), X. B. Chen (The LHAASO Collaboration), X. J. Chen (The LHAASO Collaboration), X. P. Chen (The LHAASO Collaboration), Y. Chen (The LHAASO Collaboration), N. Cheng (The LHAASO Collaboration), Q. Y. Cheng (The LHAASO Collaboration), Y. D. Cheng (The LHAASO Collaboration), M. Y. Cui (The LHAASO Collaboration), S. W. Cui (The LHAASO Collaboration), X. H. Cui (The LHAASO Collaboration), Y. D. Cui (The LHAASO Collaboration), B. Z. Dai (The LHAASO Collaboration), H. L. Dai (The LHAASO Collaboration), Z. G. Dai (The LHAASO Collaboration), Danzengluobu (The LHAASO Collaboration), Y. X. Diao (The LHAASO Collaboration), A. J. Dong (The LHAASO Collaboration), X. Q. Dong (The LHAASO Collaboration), K. K. Duan (The LHAASO Collaboration), J. H. Fan (The LHAASO Collaboration), Y. Z. Fan (The LHAASO Collaboration), J. Fang (The LHAASO Collaboration), J. H. Fang (The LHAASO Collaboration), K. Fang (The LHAASO Collaboration), C. F. Feng (The LHAASO Collaboration), H. Feng (The LHAASO Collaboration), L. Feng (The LHAASO Collaboration), S. H. Feng (The LHAASO Collaboration), X. T. Feng (The LHAASO Collaboration), Y. Feng (The LHAASO Collaboration), Y. L. Feng (The LHAASO Collaboration), S. Gabici (The LHAASO Collaboration), B. Gao (The LHAASO Collaboration), Q. Gao (The LHAASO Collaboration), W. Gao (The LHAASO Collaboration), W. K. Gao (The LHAASO Collaboration), M. M. Ge (The LHAASO Collaboration), T. T. Ge (The LHAASO Collaboration), L. S. Geng (The LHAASO Collaboration), G. Giacinti (The LHAASO Collaboration), G. H. Gong (The LHAASO Collaboration), Q. B. Gou (The LHAASO Collaboration), M. H. Gu (The LHAASO Collaboration), F. L. Guo (The LHAASO Collaboration), J. Guo (The LHAASO Collaboration), K. J. Guo (The LHAASO Collaboration), X. L. Guo (The LHAASO Collaboration), Y. Q. Guo (The LHAASO Collaboration), Y. Y. Guo (The LHAASO Collaboration), R. P. Han (The LHAASO Collaboration), O. A. Hannuksela (The LHAASO Collaboration), M. Hasan (The LHAASO Collaboration), H. H. He (The LHAASO Collaboration), H. N. He (The LHAASO Collaboration), J. Y. He (The LHAASO Collaboration), X. Y. He (The LHAASO Collaboration), Y. He (The LHAASO Collaboration), S. Hernández-Cadena (The LHAASO Collaboration), B. W. Hou (The LHAASO Collaboration), C. Hou (The LHAASO Collaboration), X. Hou (The LHAASO Collaboration), H. B. Hu (The LHAASO Collaboration), S. C. Hu (The LHAASO Collaboration), C. Huang (The LHAASO Collaboration), D. H. Huang (The LHAASO Collaboration), J. J. Huang (The LHAASO Collaboration), X. L. Huang (The LHAASO Collaboration), X. T. Huang (The LHAASO Collaboration), X. Y. Huang (The LHAASO Collaboration), Y. Huang (The LHAASO Collaboration), Y. Y. Huang (The LHAASO Collaboration), A. Inventar (The LHAASO Collaboration), X. L. Ji (The LHAASO Collaboration), H. Y. Jia (The LHAASO Collaboration), K. Jia (The LHAASO Collaboration), H. B. Jiang (The LHAASO Collaboration), K. Jiang (The LHAASO Collaboration), X. W. Jiang (The LHAASO Collaboration), Z. J. Jiang (The LHAASO Collaboration), M. Jin (The LHAASO Collaboration), S. Kaci (The LHAASO Collaboration), M. M. Kang (The LHAASO Collaboration), I. Karpikov (The LHAASO Collaboration), D. Khangulyan (The LHAASO Collaboration), D. Kuleshov (The LHAASO Collaboration), K. Kurinov (The LHAASO Collaboration), Cheng Li (The LHAASO Collaboration), Cong Li (The LHAASO Collaboration), D. Li (The LHAASO Collaboration), F. Li (The LHAASO Collaboration), H. B. Li (The LHAASO Collaboration), H. C. Li (The LHAASO Collaboration), Jian Li (The LHAASO Collaboration), Jie Li (The LHAASO Collaboration), K. Li (The LHAASO Collaboration), L. Li (The LHAASO Collaboration), R. L. Li (The LHAASO Collaboration), S. D. Li (The LHAASO Collaboration), T. Y. Li (The LHAASO Collaboration), W. L. Li (The LHAASO Collaboration), X. R. Li (The LHAASO Collaboration), Y. Li (The LHAASO Collaboration), Zhe Li (The LHAASO Collaboration), Zhuo Li (The LHAASO Collaboration), E. W. Liang (The LHAASO Collaboration), Y. F. Liang (The LHAASO Collaboration), S. J. Lin (The LHAASO Collaboration), B. Liu (The LHAASO Collaboration), C. Liu (The LHAASO Collaboration), D. Liu (The LHAASO Collaboration), D. B. Liu (The LHAASO Collaboration), H. Liu (The LHAASO Collaboration), J. Liu (The LHAASO Collaboration), J. L. Liu (The LHAASO Collaboration), J. R. Liu (The LHAASO Collaboration), M. Y. Liu (The LHAASO Collaboration), R. Y. Liu (The LHAASO Collaboration), S. M. Liu (The LHAASO Collaboration), W. Liu (The LHAASO Collaboration), X. Liu (The LHAASO Collaboration), Y. Liu (The LHAASO Collaboration), Y. Liu (The LHAASO Collaboration), Y. N. Liu (The LHAASO Collaboration), Y. Q. Lou (The LHAASO Collaboration), Q. Luo (The LHAASO Collaboration), Y. Luo (The LHAASO Collaboration), H. K. Lv (The LHAASO Collaboration), B. Q. Ma (The LHAASO Collaboration), L. L. Ma (The LHAASO Collaboration), X. H. Ma (The LHAASO Collaboration), I. O. Maliy (The LHAASO Collaboration), J. R. Mao (The LHAASO Collaboration), Z. Min (The LHAASO Collaboration), W. Mitthumsiri (The LHAASO Collaboration), Y. Mizuno (The LHAASO Collaboration), G. B. Mou (The LHAASO Collaboration), A. Neronov (The LHAASO Collaboration), K. C. Y. Ng (The LHAASO Collaboration), M. Y. Ni (The LHAASO Collaboration), L. Nie (The LHAASO Collaboration), L. J. Ou (The LHAASO Collaboration), Z. W. Ou (The LHAASO Collaboration), P. Pattarakijwanich (The LHAASO Collaboration), Z. Y. Pei (The LHAASO Collaboration), D. Y. Peng (The LHAASO Collaboration), J. C. Qi (The LHAASO Collaboration), M. Y. Qi (The LHAASO Collaboration), J. J. Qin (The LHAASO Collaboration), D. Qu (The LHAASO Collaboration), A. Raza (The LHAASO Collaboration), C. Y. Ren (The LHAASO Collaboration), D. Ruffolo (The LHAASO Collaboration), A. Sáiz (The LHAASO Collaboration), D. Savchenko (The LHAASO Collaboration), D. Semikoz (The LHAASO Collaboration), L. Shao (The LHAASO Collaboration), O. Shchegolev (The LHAASO Collaboration), Y. Z. Shen (The LHAASO Collaboration), X. D. Sheng (The LHAASO Collaboration), Z. D. Shi (The LHAASO Collaboration), F. W. Shu (The LHAASO Collaboration), H. C. Song (The LHAASO Collaboration), Yu. V. Stenkin (The LHAASO Collaboration), Y. Su (The LHAASO Collaboration), D. X. Sun (The LHAASO Collaboration), H. Sun (The LHAASO Collaboration), J. X. Sun (The LHAASO Collaboration), Q. N. Sun (The LHAASO Collaboration), X. N. Sun (The LHAASO Collaboration), Z. B. Sun (The LHAASO Collaboration), N. H. Tabasam (The LHAASO Collaboration), J. Takata (The LHAASO Collaboration), P. H. T. Tam (The LHAASO Collaboration), H. B. Tan (The LHAASO Collaboration), Q. W. Tang (The LHAASO Collaboration), R. Tang (The LHAASO Collaboration), Z. B. Tang (The LHAASO Collaboration), W. W. Tian (The LHAASO Collaboration), C. N. Tong (The LHAASO Collaboration), L. H. Wan (The LHAASO Collaboration), C. Wang (The LHAASO Collaboration), D. H. Wang (The LHAASO Collaboration), G. W. Wang (The LHAASO Collaboration), H. G. Wang (The LHAASO Collaboration), J. C. Wang (The LHAASO Collaboration), K. Wang (The LHAASO Collaboration), Kai Wang (The LHAASO Collaboration), Kai Wang (The LHAASO Collaboration), L. P. Wang (The LHAASO Collaboration), L. Y. Wang (The LHAASO Collaboration), L. Y. Wang (The LHAASO Collaboration), R. Wang (The LHAASO Collaboration), W. Wang (The LHAASO Collaboration), X. G. Wang (The LHAASO Collaboration), X. J. Wang (The LHAASO Collaboration), X. Y. Wang (The LHAASO Collaboration), Y. Wang (The LHAASO Collaboration), Y. D. Wang (The LHAASO Collaboration), Z. H. Wang (The LHAASO Collaboration), Z. X. Wang (The LHAASO Collaboration), Zheng Wang (The LHAASO Collaboration), D. M. Wei (The LHAASO Collaboration), J. J. Wei (The LHAASO Collaboration), Y. J. Wei (The LHAASO Collaboration), T. Wen (The LHAASO Collaboration), S. S. Weng (The LHAASO Collaboration), C. Y. Wu (The LHAASO Collaboration), H. R. Wu (The LHAASO Collaboration), Q. W. Wu (The LHAASO Collaboration), S. Wu (The LHAASO Collaboration), X. F. Wu (The LHAASO Collaboration), Y. S. Wu (The LHAASO Collaboration), S. Q. Xi (The LHAASO Collaboration), J. Xia (The LHAASO Collaboration), J. J. Xia (The LHAASO Collaboration), G. M. Xiang (The LHAASO Collaboration), D. X. Xiao (The LHAASO Collaboration), G. Xiao (The LHAASO Collaboration), Y. F. Xiao (The LHAASO Collaboration), Y. L. Xin (The LHAASO Collaboration), H. D. Xing (The LHAASO Collaboration), Y. Xing (The LHAASO Collaboration), D. R. Xiong (The LHAASO Collaboration), B. N. Xu (The LHAASO Collaboration), C. Y. Xu (The LHAASO Collaboration), D. L. Xu (The LHAASO Collaboration), R. F. Xu (The LHAASO Collaboration), R. X. Xu (The LHAASO Collaboration), S. S. Xu (The LHAASO Collaboration), W. L. Xu (The LHAASO Collaboration), L. Xue (The LHAASO Collaboration), D. H. Yan (The LHAASO Collaboration), T. Yan (The LHAASO Collaboration), C. W. Yang (The LHAASO Collaboration), C. Y. Yang (The LHAASO Collaboration), F. F. Yang (The LHAASO Collaboration), L. L. Yang (The LHAASO Collaboration), M. J. Yang (The LHAASO Collaboration), R. Z. Yang (The LHAASO Collaboration), W. X. Yang (The LHAASO Collaboration), Z. H. Yang (The LHAASO Collaboration), Z. G. Yao (The LHAASO Collaboration), X. A. Ye (The LHAASO Collaboration), L. Q. Yin (The LHAASO Collaboration), N. Yin (The LHAASO Collaboration), X. H. You (The LHAASO Collaboration), Z. Y. You (The LHAASO Collaboration), Q. Yuan (The LHAASO Collaboration), H. Yue (The LHAASO Collaboration), H. D. Zeng (The LHAASO Collaboration), T. X. Zeng (The LHAASO Collaboration), W. Zeng (The LHAASO Collaboration), X. T. Zeng (The LHAASO Collaboration), M. Zha (The LHAASO Collaboration), B. B. Zhang (The LHAASO Collaboration), B. T. Zhang (The LHAASO Collaboration), C. Zhang (The LHAASO Collaboration), H. Zhang (The LHAASO Collaboration), H. M. Zhang (The LHAASO Collaboration), H. Y. Zhang (The LHAASO Collaboration), J. L. Zhang (The LHAASO Collaboration), J. Y. Zhang (The LHAASO Collaboration), Li Zhang (The LHAASO Collaboration), P. F. Zhang (The LHAASO Collaboration), R. Zhang (The LHAASO Collaboration), S. R. Zhang (The LHAASO Collaboration), S. S. Zhang (The LHAASO Collaboration), S. Y. Zhang (The LHAASO Collaboration), W. Zhang (The LHAASO Collaboration), W. Y. Zhang (The LHAASO Collaboration), X. Zhang (The LHAASO Collaboration), X. P. Zhang (The LHAASO Collaboration), Yi Zhang (The LHAASO Collaboration), Yong Zhang (The LHAASO Collaboration), Z. P. Zhang (The LHAASO Collaboration), J. Zhao (The LHAASO Collaboration), L. Zhao (The LHAASO Collaboration), L. Z. Zhao (The LHAASO Collaboration), S. P. Zhao (The LHAASO Collaboration), X. H. Zhao (The LHAASO Collaboration), Z. H. Zhao (The LHAASO Collaboration), F. Zheng (The LHAASO Collaboration), T. C. Zheng (The LHAASO Collaboration), B. Zhou (The LHAASO Collaboration), H. Zhou (The LHAASO Collaboration), J. N. Zhou (The LHAASO Collaboration), M. Zhou (The LHAASO Collaboration), P. Zhou (The LHAASO Collaboration), R. Zhou (The LHAASO Collaboration), X. X. Zhou (The LHAASO Collaboration), X. X. Zhou (The LHAASO Collaboration), B. Y. Zhu (The LHAASO Collaboration), C. G. Zhu (The LHAASO Collaboration), F. R. Zhu (The LHAASO Collaboration), H. Zhu (The LHAASO Collaboration), K. J. Zhu (The LHAASO Collaboration), Y. C. Zou (The LHAASO Collaboration), X. Zuo (The LHAASO Collaboration), Y. Li

Published 2026-04-27

📖 3 min read☕ Coffee break read

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Original authors: Zhen Cao (The LHAASO Collaboration), F. Aharonian (The LHAASO Collaboration), Y. X. Bai (The LHAASO Collaboration), Y. W. Bao (The LHAASO Collaboration), D. Bastieri (The LHAASO Collaboration), X. J. Bi (The LHAASO Collaboration), Y. J. Bi (The LHAASO Collaboration), W. Bian (The LHAASO Collaboration), J. Blunier (The LHAASO Collaboration), A. V. Bukevich (The LHAASO Collaboration), C. M. Cai (The LHAASO Collaboration), Y. Y. Cai (The LHAASO Collaboration), W. Y. Cao (The LHAASO Collaboration), Zhe Cao (The LHAASO Collaboration), J. Chang (The LHAASO Collaboration), J. F. Chang (The LHAASO Collaboration), E. S. Chen (The LHAASO Collaboration), G. H. Chen (The LHAASO Collaboration), H. K. Chen (The LHAASO Collaboration), L. F. Chen (The LHAASO Collaboration), Liang Chen (The LHAASO Collaboration), Long Chen (The LHAASO Collaboration), M. J. Chen (The LHAASO Collaboration), M. L. Chen (The LHAASO Collaboration), Q. H. Chen (The LHAASO Collaboration), S. Chen (The LHAASO Collaboration), S. H. Chen (The LHAASO Collaboration), S. Z. Chen (The LHAASO Collaboration), T. L. Chen (The LHAASO Collaboration), X. B. Chen (The LHAASO Collaboration), X. J. Chen (The LHAASO Collaboration), X. P. Chen (The LHAASO Collaboration), Y. Chen (The LHAASO Collaboration), N. Cheng (The LHAASO Collaboration), Q. Y. Cheng (The LHAASO Collaboration), Y. D. Cheng (The LHAASO Collaboration), M. Y. Cui (The LHAASO Collaboration), S. W. Cui (The LHAASO Collaboration), X. H. Cui (The LHAASO Collaboration), Y. D. Cui (The LHAASO Collaboration), B. Z. Dai (The LHAASO Collaboration), H. L. Dai (The LHAASO Collaboration), Z. G. Dai (The LHAASO Collaboration), Danzengluobu (The LHAASO Collaboration), Y. X. Diao (The LHAASO Collaboration), A. J. Dong (The LHAASO Collaboration), X. Q. Dong (The LHAASO Collaboration), K. K. Duan (The LHAASO Collaboration), J. H. Fan (The LHAASO Collaboration), Y. Z. Fan (The LHAASO Collaboration), J. Fang (The LHAASO Collaboration), J. H. Fang (The LHAASO Collaboration), K. Fang (The LHAASO Collaboration), C. F. Feng (The LHAASO Collaboration), H. Feng (The LHAASO Collaboration), L. Feng (The LHAASO Collaboration), S. H. Feng (The LHAASO Collaboration), X. T. Feng (The LHAASO Collaboration), Y. Feng (The LHAASO Collaboration), Y. L. Feng (The LHAASO Collaboration), S. Gabici (The LHAASO Collaboration), B. Gao (The LHAASO Collaboration), Q. Gao (The LHAASO Collaboration), W. Gao (The LHAASO Collaboration), W. K. Gao (The LHAASO Collaboration), M. M. Ge (The LHAASO Collaboration), T. T. Ge (The LHAASO Collaboration), L. S. Geng (The LHAASO Collaboration), G. Giacinti (The LHAASO Collaboration), G. H. Gong (The LHAASO Collaboration), Q. B. Gou (The LHAASO Collaboration), M. H. Gu (The LHAASO Collaboration), F. L. Guo (The LHAASO Collaboration), J. Guo (The LHAASO Collaboration), K. J. Guo (The LHAASO Collaboration), X. L. Guo (The LHAASO Collaboration), Y. Q. Guo (The LHAASO Collaboration), Y. Y. Guo (The LHAASO Collaboration), R. P. Han (The LHAASO Collaboration), O. A. Hannuksela (The LHAASO Collaboration), M. Hasan (The LHAASO Collaboration), H. H. He (The LHAASO Collaboration), H. N. He (The LHAASO Collaboration), J. Y. He (The LHAASO Collaboration), X. Y. He (The LHAASO Collaboration), Y. He (The LHAASO Collaboration), S. Hernández-Cadena (The LHAASO Collaboration), B. W. Hou (The LHAASO Collaboration), C. Hou (The LHAASO Collaboration), X. Hou (The LHAASO Collaboration), H. B. Hu (The LHAASO Collaboration), S. C. Hu (The LHAASO Collaboration), C. Huang (The LHAASO Collaboration), D. H. Huang (The LHAASO Collaboration), J. J. Huang (The LHAASO Collaboration), X. L. Huang (The LHAASO Collaboration), X. T. Huang (The LHAASO Collaboration), X. Y. Huang (The LHAASO Collaboration), Y. Huang (The LHAASO Collaboration), Y. Y. Huang (The LHAASO Collaboration), A. Inventar (The LHAASO Collaboration), X. L. Ji (The LHAASO Collaboration), H. Y. Jia (The LHAASO Collaboration), K. Jia (The LHAASO Collaboration), H. B. Jiang (The LHAASO Collaboration), K. Jiang (The LHAASO Collaboration), X. W. Jiang (The LHAASO Collaboration), Z. J. Jiang (The LHAASO Collaboration), M. Jin (The LHAASO Collaboration), S. Kaci (The LHAASO Collaboration), M. M. Kang (The LHAASO Collaboration), I. Karpikov (The LHAASO Collaboration), D. Khangulyan (The LHAASO Collaboration), D. Kuleshov (The LHAASO Collaboration), K. Kurinov (The LHAASO Collaboration), Cheng Li (The LHAASO Collaboration), Cong Li (The LHAASO Collaboration), D. Li (The LHAASO Collaboration), F. Li (The LHAASO Collaboration), H. B. Li (The LHAASO Collaboration), H. C. Li (The LHAASO Collaboration), Jian Li (The LHAASO Collaboration), Jie Li (The LHAASO Collaboration), K. Li (The LHAASO Collaboration), L. Li (The LHAASO Collaboration), R. L. Li (The LHAASO Collaboration), S. D. Li (The LHAASO Collaboration), T. Y. Li (The LHAASO Collaboration), W. L. Li (The LHAASO Collaboration), X. R. Li (The LHAASO Collaboration), Y. Li (The LHAASO Collaboration), Zhe Li (The LHAASO Collaboration), Zhuo Li (The LHAASO Collaboration), E. W. Liang (The LHAASO Collaboration), Y. F. Liang (The LHAASO Collaboration), S. J. Lin (The LHAASO Collaboration), B. Liu (The LHAASO Collaboration), C. Liu (The LHAASO Collaboration), D. Liu (The LHAASO Collaboration), D. B. Liu (The LHAASO Collaboration), H. Liu (The LHAASO Collaboration), J. Liu (The LHAASO Collaboration), J. L. Liu (The LHAASO Collaboration), J. R. Liu (The LHAASO Collaboration), M. Y. Liu (The LHAASO Collaboration), R. Y. Liu (The LHAASO Collaboration), S. M. Liu (The LHAASO Collaboration), W. Liu (The LHAASO Collaboration), X. Liu (The LHAASO Collaboration), Y. Liu (The LHAASO Collaboration), Y. Liu (The LHAASO Collaboration), Y. N. Liu (The LHAASO Collaboration), Y. Q. Lou (The LHAASO Collaboration), Q. Luo (The LHAASO Collaboration), Y. Luo (The LHAASO Collaboration), H. K. Lv (The LHAASO Collaboration), B. Q. Ma (The LHAASO Collaboration), L. L. Ma (The LHAASO Collaboration), X. H. Ma (The LHAASO Collaboration), I. O. Maliy (The LHAASO Collaboration), J. R. Mao (The LHAASO Collaboration), Z. Min (The LHAASO Collaboration), W. Mitthumsiri (The LHAASO Collaboration), Y. Mizuno (The LHAASO Collaboration), G. B. Mou (The LHAASO Collaboration), A. Neronov (The LHAASO Collaboration), K. C. Y. Ng (The LHAASO Collaboration), M. Y. Ni (The LHAASO Collaboration), L. Nie (The LHAASO Collaboration), L. J. Ou (The LHAASO Collaboration), Z. W. Ou (The LHAASO Collaboration), P. Pattarakijwanich (The LHAASO Collaboration), Z. Y. Pei (The LHAASO Collaboration), D. Y. Peng (The LHAASO Collaboration), J. C. Qi (The LHAASO Collaboration), M. Y. Qi (The LHAASO Collaboration), J. J. Qin (The LHAASO Collaboration), D. Qu (The LHAASO Collaboration), A. Raza (The LHAASO Collaboration), C. Y. Ren (The LHAASO Collaboration), D. Ruffolo (The LHAASO Collaboration), A. Sáiz (The LHAASO Collaboration), D. Savchenko (The LHAASO Collaboration), D. Semikoz (The LHAASO Collaboration), L. Shao (The LHAASO Collaboration), O. Shchegolev (The LHAASO Collaboration), Y. Z. Shen (The LHAASO Collaboration), X. D. Sheng (The LHAASO Collaboration), Z. D. Shi (The LHAASO Collaboration), F. W. Shu (The LHAASO Collaboration), H. C. Song (The LHAASO Collaboration), Yu. V. Stenkin (The LHAASO Collaboration), Y. Su (The LHAASO Collaboration), D. X. Sun (The LHAASO Collaboration), H. Sun (The LHAASO Collaboration), J. X. Sun (The LHAASO Collaboration), Q. N. Sun (The LHAASO Collaboration), X. N. Sun (The LHAASO Collaboration), Z. B. Sun (The LHAASO Collaboration), N. H. Tabasam (The LHAASO Collaboration), J. Takata (The LHAASO Collaboration), P. H. T. Tam (The LHAASO Collaboration), H. B. Tan (The LHAASO Collaboration), Q. W. Tang (The LHAASO Collaboration), R. Tang (The LHAASO Collaboration), Z. B. Tang (The LHAASO Collaboration), W. W. Tian (The LHAASO Collaboration), C. N. Tong (The LHAASO Collaboration), L. H. Wan (The LHAASO Collaboration), C. Wang (The LHAASO Collaboration), D. H. Wang (The LHAASO Collaboration), G. W. Wang (The LHAASO Collaboration), H. G. Wang (The LHAASO Collaboration), J. C. Wang (The LHAASO Collaboration), K. Wang (The LHAASO Collaboration), Kai Wang (The LHAASO Collaboration), Kai Wang (The LHAASO Collaboration), L. P. Wang (The LHAASO Collaboration), L. Y. Wang (The LHAASO Collaboration), L. Y. Wang (The LHAASO Collaboration), R. Wang (The LHAASO Collaboration), W. Wang (The LHAASO Collaboration), X. G. Wang (The LHAASO Collaboration), X. J. Wang (The LHAASO Collaboration), X. Y. Wang (The LHAASO Collaboration), Y. Wang (The LHAASO Collaboration), Y. D. Wang (The LHAASO Collaboration), Z. H. Wang (The LHAASO Collaboration), Z. X. Wang (The LHAASO Collaboration), Zheng Wang (The LHAASO Collaboration), D. M. Wei (The LHAASO Collaboration), J. J. Wei (The LHAASO Collaboration), Y. J. Wei (The LHAASO Collaboration), T. Wen (The LHAASO Collaboration), S. S. Weng (The LHAASO Collaboration), C. Y. Wu (The LHAASO Collaboration), H. R. Wu (The LHAASO Collaboration), Q. W. Wu (The LHAASO Collaboration), S. Wu (The LHAASO Collaboration), X. F. Wu (The LHAASO Collaboration), Y. S. Wu (The LHAASO Collaboration), S. Q. Xi (The LHAASO Collaboration), J. Xia (The LHAASO Collaboration), J. J. Xia (The LHAASO Collaboration), G. M. Xiang (The LHAASO Collaboration), D. X. Xiao (The LHAASO Collaboration), G. Xiao (The LHAASO Collaboration), Y. F. Xiao (The LHAASO Collaboration), Y. L. Xin (The LHAASO Collaboration), H. D. Xing (The LHAASO Collaboration), Y. Xing (The LHAASO Collaboration), D. R. Xiong (The LHAASO Collaboration), B. N. Xu (The LHAASO Collaboration), C. Y. Xu (The LHAASO Collaboration), D. L. Xu (The LHAASO Collaboration), R. F. Xu (The LHAASO Collaboration), R. X. Xu (The LHAASO Collaboration), S. S. Xu (The LHAASO Collaboration), W. L. Xu (The LHAASO Collaboration), L. Xue (The LHAASO Collaboration), D. H. Yan (The LHAASO Collaboration), T. Yan (The LHAASO Collaboration), C. W. Yang (The LHAASO Collaboration), C. Y. Yang (The LHAASO Collaboration), F. F. Yang (The LHAASO Collaboration), L. L. Yang (The LHAASO Collaboration), M. J. Yang (The LHAASO Collaboration), R. Z. Yang (The LHAASO Collaboration), W. X. Yang (The LHAASO Collaboration), Z. H. Yang (The LHAASO Collaboration), Z. G. Yao (The LHAASO Collaboration), X. A. Ye (The LHAASO Collaboration), L. Q. Yin (The LHAASO Collaboration), N. Yin (The LHAASO Collaboration), X. H. You (The LHAASO Collaboration), Z. Y. You (The LHAASO Collaboration), Q. Yuan (The LHAASO Collaboration), H. Yue (The LHAASO Collaboration), H. D. Zeng (The LHAASO Collaboration), T. X. Zeng (The LHAASO Collaboration), W. Zeng (The LHAASO Collaboration), X. T. Zeng (The LHAASO Collaboration), M. Zha (The LHAASO Collaboration), B. B. Zhang (The LHAASO Collaboration), B. T. Zhang (The LHAASO Collaboration), C. Zhang (The LHAASO Collaboration), H. Zhang (The LHAASO Collaboration), H. M. Zhang (The LHAASO Collaboration), H. Y. Zhang (The LHAASO Collaboration), J. L. Zhang (The LHAASO Collaboration), J. Y. Zhang (The LHAASO Collaboration), Li Zhang (The LHAASO Collaboration), P. F. Zhang (The LHAASO Collaboration), R. Zhang (The LHAASO Collaboration), S. R. Zhang (The LHAASO Collaboration), S. S. Zhang (The LHAASO Collaboration), S. Y. Zhang (The LHAASO Collaboration), W. Zhang (The LHAASO Collaboration), W. Y. Zhang (The LHAASO Collaboration), X. Zhang (The LHAASO Collaboration), X. P. Zhang (The LHAASO Collaboration), Yi Zhang (The LHAASO Collaboration), Yong Zhang (The LHAASO Collaboration), Z. P. Zhang (The LHAASO Collaboration), J. Zhao (The LHAASO Collaboration), L. Zhao (The LHAASO Collaboration), L. Z. Zhao (The LHAASO Collaboration), S. P. Zhao (The LHAASO Collaboration), X. H. Zhao (The LHAASO Collaboration), Z. H. Zhao (The LHAASO Collaboration), F. Zheng (The LHAASO Collaboration), T. C. Zheng (The LHAASO Collaboration), B. Zhou (The LHAASO Collaboration), H. Zhou (The LHAASO Collaboration), J. N. Zhou (The LHAASO Collaboration), M. Zhou (The LHAASO Collaboration), P. Zhou (The LHAASO Collaboration), R. Zhou (The LHAASO Collaboration), X. X. Zhou (The LHAASO Collaboration), X. X. Zhou (The LHAASO Collaboration), B. Y. Zhu (The LHAASO Collaboration), C. G. Zhu (The LHAASO Collaboration), F. R. Zhu (The LHAASO Collaboration), H. Zhu (The LHAASO Collaboration), K. J. Zhu (The LHAASO Collaboration), Y. C. Zou (The LHAASO Collaboration), X. Zuo (The LHAASO Collaboration), Y. Li

Original paper licensed under CC BY 4.0 (http://creativecommons.org/licenses/by/4.0/). ✨ This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer

The Cosmic Spotlight: How Supernova Remnants Reveal the Universe's Fastest Particles

Imagine you are standing in a pitch-black forest at night. You can’t see the trees, the ground, or the paths. However, suddenly, a massive, invisible wind begins to blow. As this wind hits a dense thicket of bushes, you hear a loud rustling sound. Even though you can’t see the wind itself, that sound tells you exactly where the wind is blowing and how strong it is.

This scientific paper is essentially about astronomers finding the "rustling" of the universe.

The Mystery: The Invisible Speedsters

For decades, scientists have known that our galaxy is filled with Cosmic Rays—tiny, incredibly energetic particles traveling at nearly the speed of light. We know they exist, but we’ve had a hard time finding their "engines." We suspected that Supernova Remnants (SNRs)—the exploding leftovers of dead stars—were the massive engines accelerating these particles to extreme speeds.

The problem? These particles are invisible. They don't glow like a lightbulb; they are more like a silent, invisible gust of wind.

The Discovery: The Cosmic "Rustling"

Using a massive, high-altitude observatory in China called LHAASO (which acts like a giant, ultra-sensitive ear for the sky), researchers looked at two specific "explosion sites" in our galaxy: G150.3+4.5 and $\gamma$ -Cygni.

They didn't see the particles themselves, but they saw something even better: Ultra-high-energy $\gamma$ -rays.

Think of these $\gamma$ -rays as the "sparks" created when the invisible cosmic wind (the particles) slams into a "bush" (a massive cloud of cold gas called a Molecular Cloud). When these invisible particles hit the gas clouds, they create a flash of light. By looking at where these flashes happen, scientists can map out exactly where the invisible particles are traveling.

The "Aha!" Moment: The PeVatrons

The most exciting part of this paper is the speed. The researchers found evidence that these engines are capable of accelerating particles to PeV (Peta-electronvolt) energies.

To put that in perspective: if a standard cosmic ray were a gentle breeze, a PeV particle is a supersonic jet engine.

For a long time, scientists debated whether supernova remnants were actually powerful enough to reach these "PeV" speeds. This paper provides the "smoking gun" evidence. By seeing these ultra-high-energy flashes hitting nearby gas clouds, they have confirmed that these supernova remnants are indeed "PeVatrons"—the ultimate particle accelerators of our galaxy.

Summary in a Nutshell

The Engine: Dying stars (Supernova Remnants) acting like giant cosmic particle accelerators.
The Wind: Invisible, ultra-fast particles (Cosmic Rays).
The Bush: Massive clouds of gas floating in space.
The Sound/Light: High-energy $\gamma$ -rays produced when the "wind" hits the "bush."
The Result: We finally have proof that these star explosions are powerful enough to create the most energetic particles in the Milky Way.

Technical Summary: Ultra-high-energy $\gamma$ -ray imprints from PeV particles accelerated by supernova remnants

1. Problem Statement

A fundamental question in astrophysics is the origin of Galactic cosmic rays (CRs) and the mechanism behind the "spectral knee" located near $\sim 3$ PeV. While Supernova Remnants (SNRs) are widely considered the primary candidates for accelerating CRs up to this energy, direct evidence of "PeVatrons"—accelerators capable of reaching PeV energies—has remained elusive. Previous observations of ultra-high-energy (UHE) $\gamma$ -rays often involved sources with powerful Pulsar Wind Nebulae (PWNe), making it difficult to distinguish whether the emission was leptonic (from electrons) or hadronic (from protons).

2. Methodology

The researchers utilized data from the Large High Altitude Air Shower Observatory (LHAASO), specifically combining data from the Water Cherenkov Detector Array (WCDA) and the KM2A array.

Target Sources: Two middle-aged, shell-type SNRs: G150.3+4.5 and $\gamma$ -Cygni.
Analysis Technique: A 3-dimensional likelihood fitting method was employed to simultaneously fit the spatial morphology (using 2D Gaussian distributions) and the energy spectrum (using a power-law with an exponential cutoff, PLEcut).
Background Estimation: The "direct integral method" was used to estimate the cosmic-ray background.
Modeling: A hybrid model was constructed to account for both:
- Leptonic processes: Inverse Compton (IC) scattering of electrons off background radiation fields (CMB, infrared, and optical).
- Hadronic processes: $\pi^0$ -decay resulting from the collision of high-energy CR protons with ambient molecular clouds (MCs).
Multi-wavelength Correlation: The $\gamma$ -ray flux was spatially correlated with radio continuum maps (tracing electrons/synchrotron) and CO molecular gas observations (tracing target material for hadronic collisions).

3. Key Contributions

Identification of Hadronic PeVatrons: The study provides the first clear evidence that the highest-energy $\gamma$ -ray emission in these specific SNRs is produced by hadronic interactions.
Morphological Differentiation: The paper demonstrates that UHE $\gamma$ -ray emission is spatially distinct from low-energy emission. While low-energy components match the SNR radio shells (leptonic/synchrotron), the high-energy components correlate with nearby molecular clouds.
Multi-component Modeling: The researchers successfully decomposed the emission into multiple components (Source A, B, and C), allowing for a nuanced understanding of particle escape and interaction.

4. Results

Detection Significance: LHAASO detected G150.3+4.5 at $29.8\sigma$ and $\gamma$ -Cygni at $48.9\sigma$ . Emission was detected even above 100 TeV.
Morphology:
- In G150.3+4.5, the low-energy component (Source A) is extended and matches the radio shell, while the high-energy component (Source B) is compact and coincides with a molecular cloud ( $\sim 5 \times 10^3 M_\odot$ ).
- In $\gamma$ -Cygni, the emission shows a similar trend, with high-energy components correlating with dense molecular gas.
Spectral Findings:
- The high-energy components (Source B) exhibit hard, curved spectra.
- The cutoff energies for the injected protons were estimated to be approximately 800 TeV, implying that the accelerated protons reach energies $\gtrsim 1$ PeV.
Correlation: A strong spatial correlation was found between the $\gamma$ -ray flux of the high-energy components and the integrated CO-traced molecular mass.

5. Significance

This work provides a "smoking gun" for the hadronic origin of ultra-high-energy $\gamma$ -rays in middle-aged SNRs. By showing that PeV particles escape the SNR shock and illuminate nearby molecular clouds, the study confirms that SNRs can indeed act as PeVatrons.

However, the study also notes a nuance: while the protons reach PeV energies, the spectral cutoff of the injection spectrum is slightly below the PeV scale. This suggests that while SNRs are major contributors to Galactic CRs, they may not be the sole dominant source for the CR spectrum well above the knee, potentially pointing toward other accelerators like the Galactic Center, massive star clusters, or microquasars.