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Evidence of Cosmic-Ray Acceleration up to Sub-PeV Energies in the Supernova Remnant IC 443

Zhen Cao1,2,3, F. Aharonian3,4,5,6, Y. X. Bai1,3, Y. W. Bao7, D. Bastieri8, X. J. Bi1,2,3, Y. J. Bi1,3, W. Bian7, A. V. Bukevich9 et al. (LHAASO Collaboration)

A. V. Bukevich9, C. M. Cai10, W. Y. Cao4, Zhe Cao11,4, J. Chang12, J. F. Chang1,3,11, A. M. Chen7, E. S. Chen1,3,*, G. H. Chen8, H. X. Chen13, Liang Chen14, Long Chen10, M. J. Chen1,3, M. L. Chen1,3,11, Q. H. Chen10, S. Chen15, S. H. Chen1,2,3, S. Z. Chen1,3, T. L. Chen16, X. B. Chen17, X. J. Chen10, Y. Chen17, N. Cheng1,3, Y. D. Cheng1,2,3, M. C. Chu18, M. Y. Cui12, S. W. Cui19, X. H. Cui20, Y. D. Cui21, B. Z. Dai15, H. L. Dai1,3,11, Z. G. Dai4, Danzengluobu16, Y. X. Diao10, X. Q. Dong1,2,3, K. K. Duan12, J. H. Fan8, Y. Z. Fan12, J. Fang15, J. H. Fang13, K. Fang1,3, C. F. Feng22, H. Feng1, L. Feng12, S. H. Feng1,3, X. T. Feng22, Y. Feng13, Y. L. Feng16, S. Gabici23, B. Gao1,3, C. D. Gao22, Q. Gao16, W. Gao1,3, W. K. Gao1,2,3, M. M. Ge15, T. T. Ge21, L. S. Geng1,3, G. Giacinti7, G. H. Gong24, Q. B. Gou1,3, M. H. Gu1,3,11, F. L. Guo14, J. Guo24, X. L. Guo10, Y. Q. Guo1,3, Y. Y. Guo12,†, Y. A. Han25, O. A. Hannuksela18, M. Hasan1,2,3, H. H. He1,2,3, H. N. He12, J. Y. He12, X. Y. He12, Y. He10, S. Hernández-Cadena7, B. W. Hou1,2,3, C. Hou1,3, X. Hou26, H. B. Hu1,2,3, S. C. Hu1,3,27, C. Huang17, D. H. Huang10, J. J. Huang1,2,3, T. Q. Huang1,3, W. J. Huang21, X. T. Huang22, X. Y. Huang12,‡, Y. Huang1,3,27, Y. Y. Huang17, X. L. Ji1,3,11, H. Y. Jia10, K. Jia22, H. B. Jiang1,3, K. Jiang11,4, X. W. Jiang1,3, Z. J. Jiang15, M. Jin10, S. Kaci7, M. M. Kang28, I. Karpikov9, D. Khangulyan1,3, D. Kuleshov9, K. Kurinov9, B. B. Li19, Cheng Li11,4, Cong Li1,3, D. Li1,2,3, F. Li1,3,11, H. B. Li1,2,3, H. C. Li1,3, Jian Li4, Jie Li1,3,11, K. Li1,3, L. Li29, R. L. Li12, S. D. Li14,2, T. Y. Li7, W. L. Li7, X. R. Li1,3, Xin Li11,4, Y. Li7, Y. Z. Li1,2,3, Zhe Li1,3, Zhuo Li30, E. W. Liang31, Y. F. Liang31, S. J. Lin21, B. Liu12, C. Liu1,3, D. Liu22, D. B. Liu7, H. Liu10, H. D. Liu25, J. Liu1,3, J. L. Liu1,3, J. R. Liu10, M. Y. Liu16, R. Y. Liu17, S. M. Liu10,§, W. Liu1,3, X. Liu10, Y. Liu8, Y. Liu10, Y. N. Liu24, Y. Q. Lou24, Q. Luo21, Y. Luo7, H. K. Lv1,3, B. Q. Ma25,30, L. L. Ma1,3, X. H. Ma1,3, J. R. Mao26, Z. Min1,3, W. Mitthumsiri32, G. B. Mou33, H. J. Mu25, A. Neronov23, K. C. Y. Ng18, M. Y. Ni12, L. Nie10, L. J. Ou8, P. Pattarakijwanich32, Z. Y. Pei8, J. C. Qi1,2,3, M. Y. Qi1,3, J. J. Qin4, A. Raza1,2,3, C. Y. Ren12, D. Ruffolo32, A. Sáiz32, D. Semikoz23, L. Shao19, O. Shchegolev9,34, Y. Z. Shen17, X. D. Sheng1,3, Z. D. Shi4, F. W. Shu29, H. C. Song30, Yu. V. Stenkin9,34, V. Stepanov9, Y. Su12, D. X. Sun4,12, H. Sun22, Q. N. Sun1,3, X. N. Sun31, Z. B. Sun35, N. H. Tabasam22, J. Takata36, P. H. T. Tam21, H. B. Tan17, Q. W. Tang29, R. Tang7, Z. B. Tang11,4, W. W. Tian2,20, C. N. Tong17, L. H. Wan21, C. Wang35, G. W. Wang4, H. G. Wang8, J. C. Wang26, K. Wang30, Kai Wang17, Kai Wang36, L. P. Wang1,2,3, L. Y. Wang1,3, L. Y. Wang19, R. Wang22, W. Wang21, X. G. Wang31, X. J. Wang10, X. Y. Wang17, Y. Wang10, Y. D. Wang1,3, Z. H. Wang28, Z. X. Wang15, Zheng Wang1,3,11, D. M. Wei12, J. J. Wei12, Y. J. Wei1,2,3, T. Wen1,3, S. S. Weng33, C. Y. Wu1,3, H. R. Wu1,3, Q. W. Wu36, S. Wu1,3, X. F. Wu12, Y. S. Wu4, S. Q. Xi1,3, J. Xia4,12, J. J. Xia10, G. M. Xiang14,2, D. X. Xiao19, G. Xiao1,3, Y. L. Xin10, Y. Xing14, D. R. Xiong26, Z. Xiong1,2,3, D. L. Xu7, R. F. Xu1,2,3, R. X. Xu30, W. L. Xu28, L. Xue22, D. H. Yan15, T. Yan1,3, C. W. Yang28, C. Y. Yang26, F. F. Yang1,3,11, L. L. Yang21, M. J. Yang1,3, R. Z. Yang4, W. X. Yang8, Z. H. Yang7, Z. G. Yao1,3, X. A. Ye12, L. Q. Yin1,3, N. Yin22, X. H. You1,3, Z. Y. You1,3, Q. Yuan12,║, H. Yue1,2,3, H. D. Zeng12,¶, T. X. Zeng1,3,11, W. Zeng15, X. T. Zeng21, M. Zha1,3, B. B. Zhang17, B. T. Zhang1,3, C. Zhang17, F. Zhang10, H. Zhang7, H. M. Zhang31, H. Y. Zhang15, J. L. Zhang20, Li Zhang15, P. F. Zhang15, P. P. Zhang4,12, R. Zhang12, S. R. Zhang19, S. S. Zhang1,3, W. Y. Zhang19, X. Zhang33, X. P. Zhang1,3, Yi Zhang1,12,**, Yong Zhang1,3, Z. P. Zhang4, J. Zhao1,3, L. Zhao11,4, L. Z. Zhao19, S. P. Zhao12, X. H. Zhao26, Z. H. Zhao4, F. Zheng35, W. J. Zhong17, B. Zhou1,3, H. Zhou7, J. N. Zhou14, M. Zhou29, P. Zhou17, R. Zhou28, X. X. Zhou1,2,3, X. X. Zhou10, B. Y. Zhu4,12, C. G. Zhu22, F. R. Zhu10, H. Zhu20, K. J. Zhu1,2,3,11, Y. C. Zou36, and X. Zuo1,3 (LHAASO Collaboration)

  • 1Key Laboratory of Particle Astrophysics and Experimental Physics Division and Computing Center, Institute of High Energy Physics, Chinese Academy of Sciences, 100049 Beijing, China
  • 2University of Chinese Academy of Sciences, 100049 Beijing, China
  • 3TIANFU Cosmic Ray Research Center, Chengdu, Sichuan, China
  • 4University of Science and Technology of China, 230026 Hefei, Anhui, China
  • 5Yerevan State University, 1 Alek Manukyan Street, Yerevan 0025, Armenia
  • 6Max-Planck-Institut for Nuclear Physics, P.O. Box 103980, 69029 Heidelberg, Germany
  • 7Tsung-Dao Lee Institute and School of Physics and Astronomy, Shanghai Jiao Tong University, 200240 Shanghai, China
  • 8Center for Astrophysics, Guangzhou University, 510006 Guangzhou, Guangdong, China
  • 9Institute for Nuclear Research of Russian Academy of Sciences, 117312 Moscow, Russia
  • 10School of Physical Science and Technology and School of Information Science and Technology, Southwest Jiaotong University, 610031 Chengdu, Sichuan, China
  • 11State Key Laboratory of Particle Detection and Electronics, Beijing, China
  • 12Key Laboratory of Dark Matter and Space Astronomy & Key Laboratory of Radio Astronomy, Purple Mountain Observatory, Chinese Academy of Sciences, 210023 Nanjing, Jiangsu, China
  • 13Research Center for Astronomical Computing, Zhejiang Laboratory, 311121 Hangzhou, Zhejiang, China
  • 14Shanghai Astronomical Observatory, Chinese Academy of Sciences, 200030 Shanghai, China
  • 15School of Physics and Astronomy, Yunnan University, 650091 Kunming, Yunnan, China
  • 16Key Laboratory of Cosmic Rays (Tibet University), Ministry of Education, 850000 Lhasa, Tibet, China
  • 17School of Astronomy and Space Science, Nanjing University, 210023 Nanjing, Jiangsu, China
  • 18Department of Physics, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
  • 19Hebei Normal University, 050024 Shijiazhuang, Hebei, China
  • 20Key Laboratory of Radio Astronomy and Technology, National Astronomical Observatories, Chinese Academy of Sciences, 100101 Beijing, China
  • 21School of Physics and Astronomy (Zhuhai) and School of Physics (Guangzhou) and Sino-French Institute of Nuclear Engineering and Technology (Zhuhai), Sun Yat-sen University, 519000 Zhuhai, 510275 Guangzhou, Guangdong, China
  • 22Institute of Frontier and Interdisciplinary Science, Shandong University, 266237 Qingdao, Shandong, China
  • 23APC, Université Paris Cité, CNRS/IN2P3, CEA/IRFU, Observatoire de Paris, 119 75205 Paris, France
  • 24Department of Engineering Physics and Department of Physics and Department of Astronomy, Tsinghua University, 100084 Beijing, China
  • 25School of Physics and Microelectronics, Zhengzhou University, 450001 Zhengzhou, Henan, China
  • 26Yunnan Observatories, Chinese Academy of Sciences, 650216 Kunming, Yunnan, China
  • 27China Center of Advanced Science and Technology, Beijing 100190, China
  • 28College of Physics, Sichuan University, 610065 Chengdu, Sichuan, China
  • 29Center for Relativistic Astrophysics and High Energy Physics, School of Physics and Materials Science and Institute of Space Science and Technology, Nanchang University, 330031 Nanchang, Jiangxi, China
  • 30School of Physics and Kavli Institute for Astronomy and Astrophysics, Peking University, 100871 Beijing, China
  • 31Guangxi Key Laboratory for Relativistic Astrophysics, School of Physical Science and Technology, Guangxi University, 530004 Nanning, Guangxi, China
  • 32Department of Physics, Faculty of Science, Mahidol University, Bangkok 10400, Thailand
  • 33School of Physics and Technology, Nanjing Normal University, 210023 Nanjing, Jiangsu, China
  • 34Moscow Institute of Physics and Technology, 141700 Moscow, Russia
  • 35National Space Science Center, Chinese Academy of Sciences, 100190 Beijing, China
  • 36School of Physics, Huazhong University of Science and Technology, Wuhan 430074, Hubei, China

  • *Contact author: chenes@ihep.ac.cn
  • †Contact author: yyguo@pmo.ac.cn
  • ‡Contact author: xyhuang@pmo.ac.cn
  • §Contact author: liusm@swjtu.edu.cn
  • ║Contact author: yuanq@pmo.ac.cn
  • Contact author: zhd@pmo.ac.cn
  • **Contact author: zhangyi@pmo.ac.cn
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Phys. Rev. Lett. 136, 161002 – Published 23 April, 2026

DOI: https://doi.org/10.1103/pxn6-qzhz

Abstract

Supernova remnants (SNRs) have been considered as the primary contributors to cosmic rays (CRs) in our Galaxy. However, the maximum energy of particles that can be accelerated by shocks of SNRs is uncertain, and SNRs’ contribution to CRs around PeV energies is unclear. In this Letter, we present observations of high-energy γ-ray emission from the SNR IC 443 using the Large High Altitude Air Shower Observatory (LHAASO). The morphological analysis reveals a pointlike source whose location and spectrum are consistent with those of the Fermi-LAT-detected compact source with π0-decay signature, and a more extended source that is associated with a newly discovered Fermi source. The spectrum of the point source can be described by a power-law function with an index of ∼3.0, extending beyond ∼30  TeV without apparent cutoff. Assuming a hadronic origin of the γ-ray emission, the 95% lower limit of accelerated protons reaches about 300 TeV. The extended source might be associated with IC 443, SNR G189.6+3.3, or the putative pulsar wind nebula CXOU J061705.3+222127, and can be explained by either a hadronic or a leptonic model with particles reaching hundreds of TeV. These LHAASO results provide compelling evidence that sub-PeV CRs can be accelerated efficiently by shocks of SNRs.

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Physics Subject Headings (PhySH)

synopsis

Pinpointing a Source of PeV Cosmic Rays

Published 23 April, 2026

Recently detected gamma rays are best accounted for by relativistic protons accelerated by a millennia-old supernova.

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Phys. Rev. Lett. 136, 161002– Published 23 April, 2026
  • Received 30 October 2025
  • Revised 25 December 2025
  • Accepted 4 March 2026
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