First detection of ultra-high energy emission from gamma-ray binary LS I +61 303
High Energy Astrophysical Phenomena
2026-03-12 v3
Abstract
We report the first detection of gamma-ray emission up to ultra-high-energy (UHE; 100 TeV) emission from the prototypical gamma-ray binary system LS I +61 303 using data from the Large High Altitude Air Shower Observatory (LHAASO). It is detected with significances of 9.2 in WCDA (1.4--30.5 TeV) and 6.2 in KM2A (25--267 TeV); in KM2A alone we identify 16 photon-like events above 100 TeV against an estimated 5.1 background events, corresponding to a 3.8 detection. These results provide compelling evidence of extreme particle acceleration in LS I +61 303. Furthermore, we observe orbital modulation at 3.9 confidence level, between 25 and 100 TeV, with a hint that the orbital modulation is energy-dependent. These features can be understood in a composite scenario in which leptonic and hadronic processes jointly contribute.
Keywords
Cite
@article{arxiv.2510.23345,
title = {First detection of ultra-high energy emission from gamma-ray binary LS I +61 303},
author = {Zhen Cao and F. Aharonian and Y. X. Bai and Y. W. Bao and D. Bastieri and X. J. Bi and Y. J. Bi and W. Bian and J. Blunier and A. V. Bukevich and C. M. Cai and Y. Y. Cai and W. Y. Cao and Zhe Cao and J. Chang and J. F. Chang and E. S. Chen and G. H. Chen and H. K. Chen and L. F. Chen and Liang Chen and Long Chen and M. J. Chen and M. L. Chen and Q. H. Chen and S. Chen and S. H. Chen and S. Z. Chen and T. L. Chen and X. B. Chen and X. J. Chen and X. P. Chen and Y. Chen and N. Cheng and Q. Y. Cheng and Y. D. Cheng and M. Y. Cui and S. W. Cui and X. H. Cui and Y. D. Cui and B. Z. Dai and H. L. Dai and Z. G. Dai and Danzengluobu and Y. X. Diao and A. J. Dong and X. Q. Dong and K. K. Duan and J. H. Fan and Y. Z. Fan and J. Fang and J. H. Fang and K. Fang and C. F. Feng and H. Feng and L. Feng and S. H. Feng and X. T. Feng and Y. Feng and Y. L. Feng and S. Gabici and B. Gao and Q. Gao and W. Gao and W. K. Gao and M. M. Ge and T. T. Ge and L. S. Geng and G. Giacinti and G. H. Gong and Q. B. Gou and M. H. Gu and F. L. Guo and J. Guo and K. J. Guo and X. L. Guo and Y. Q. Guo and Y. Y. Guo and R. P. Han and O. A. Hannuksela and M. Hasan and H. H. He and H. N. He and J. Y. He and X. Y. He and Y. He and S. Hernández-Cadena and B. W. Hou and C. Hou and X. Hou and H. B. Hu and S. C. Hu and C. Huang and D. H. Huang and J. J. Huang and X. L. Huang and X. T. Huang and X. Y. Huang and Y. Huang and Y. Y. Huang and A. Inventar and X. L. Ji and H. Y. Jia and K. Jia and H. B. Jiang and K. Jiang and X. W. Jiang and Z. J. Jiang and M. Jin and S. Kaci and M. M. Kang and I. Karpikov and D. Khangulyan and D. Kuleshov and K. Kurinov and Cheng Li and Cong Li and D. Li and F. Li and H. B. Li and H. C. Li and Jian Li and Jie Li and K. Li and L. Li and R. L. Li and S. D. Li and T. Y. Li and W. L. Li and X. R. Li and Y. Li and Zhe Li and Zhuo Li and E. W. Liang and Y. F. Liang and S. J. Lin and B. Liu and C. Liu and D. Liu and D. B. Liu and H. Liu and J. Liu and J. L. Liu and J. R. Liu and M. Y. Liu and R. Y. Liu and S. M. Liu and W. Liu and X. Liu and Y. Liu and Y. Liu and Y. N. Liu and Y. Q. Lou and Q. Luo and Y. Luo and H. K. Lv and B. Q. Ma and L. L. Ma and X. H. Ma and I. O. Maliy and J. R. Mao and Z. Min and W. Mitthumsiri and Y. Mizuno and G. B. Mou and A. Neronov and K. C. Y. Ng and M. Y. Ni and L. Nie and L. J. Ou and Z. W. Ou and P. Pattarakijwanich and Z. Y. Pei and D. Y. Peng and J. C. Qi and M. Y. Qi and J. J. Qin and D. Qu and A. Raza and C. Y. Ren and D. Ruffolo and A. Sáiz and D. Savchenko and D. Semikoz and L. Shao and O. Shchegolev and Y. Z. Shen and X. D. Sheng and Z. D. Shi and F. W. Shu and H. C. Song and Yu. V. Stenkin and Y. Su and D. X. Sun and H. Sun and J. X. Sun and Q. N. Sun and X. N. Sun and Z. B. Sun and N. H. Tabasam and J. Takata and P. H. T. Tam and H. B. Tan and Q. W. Tang and R. Tang and Z. B. Tang and W. W. Tian and C. N. Tong and L. H. Wan and C. Wang and D. H. Wang and G. W. Wang and H. G. Wang and J. C. Wang and K. Wang and Kai Wang and Kai Wang and L. P. Wang and L. Y. Wang and L. Y. Wang and R. Wang and W. Wang and X. G. Wang and X. J. Wang and X. Y. Wang and Y. Wang and Y. D. Wang and Z. H. Wang and Z. X. Wang and Zheng Wang and D. M. Wei and J. J. Wei and Y. J. Wei and T. Wen and S. S. Weng and C. Y. Wu and H. R. Wu and Q. W. Wu and S. Wu and X. F. Wu and Y. S. Wu and S. Q. Xi and J. Xia and J. J. Xia and G. M. Xiang and D. X. Xiao and G. Xiao and Y. F. Xiao and Y. L. Xin and H. D. Xing and Y. Xing and D. R. Xiong and B. N. Xu and C. Y. Xu and D. L. Xu and R. F. Xu and R. X. Xu and S. S. Xu and W. L. Xu and L. Xue and D. H. Yan and T. Yan and C. W. Yang and C. Y. Yang and F. F. Yang and L. L. Yang and M. J. Yang and R. Z. Yang and W. X. Yang and Z. H. Yang and Z. G. Yao and X. A. Ye and L. Q. Yin and N. Yin and X. H. You and Z. Y. You and Q. Yuan and H. Yue and H. D. Zeng and T. X. Zeng and W. Zeng and X. T. Zeng and M. Zha and B. B. Zhang and B. T. Zhang and C. Zhang and H. Zhang and H. M. Zhang and H. Y. Zhang and J. L. Zhang and J. Y. Zhang and Li Zhang and P. F. Zhang and R. Zhang and S. R. Zhang and S. S. Zhang and S. Y. Zhang and W. Zhang and W. Y. Zhang and X. Zhang and X. P. Zhang and Yi Zhang and Yong Zhang and Z. P. Zhang and J. Zhao and L. Zhao and L. Z. Zhao and S. P. Zhao and X. H. Zhao and Z. H. Zhao and F. Zheng and T. C. Zheng and B. Zhou and H. Zhou and J. N. Zhou and M. Zhou and P. Zhou and R. Zhou and X. X. Zhou and X. X. Zhou and B. Y. Zhu and C. G. Zhu and F. R. Zhu and H. Zhu and K. J. Zhu and Y. C. Zou and X. Zuo},
journal= {arXiv preprint arXiv:2510.23345},
year = {2026}
}
Comments
14 pages, 7 figures, 1 table, accepted for publication in PRL