Extreme PeV Accelerator Associated with GRS 1915+105

Abstract Microquasars, binary systems featuring relativistic jets, have emerged as sources for particle acceleration beyond PeV energies. We present a study of the broadband γ -ray emission from one of the most prominent Galactic microquasars, GRS 1915+105, based on data accumulated by LHAASO and Fermi Large Area Telescope over 4 and 17 yr, respectively. A joint analysis of LHAASO-WCDA and LHAASO-KM2A data reveals extended γ -ray emission whose centroid appears significantly shifted, by ∼0 . ° 13, from the binary system and its jets. The spectral energy distribution is well described by a curved spectrum with progressive steepening that can be described by a log-parabola function with no evidence for a sharp cutoff, consistent with parent particles reaching multi-PeV energies and an extreme acceleration efficiency approaching the limit set by the available potential drop across the source. Several features, most notably the shift of the emission and single power-law spectrum down to GeV band, favor radiation by cosmic rays accelerated in the source interacting with the dense ambient medium. Our spectral modeling implies that at least a few percent of the jet mechanical power is transferred to protons, whose maximum energy reaches beyond 5 PeV. These results strengthen the case for microquasars as exceptionally efficient accelerators in our Galaxy.

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Journal
The Astrophysical Journal Letters
Published
2026-10-29
DOI
https://doi.org/10.3847/2041-8213/aeaa27
Primary Topic
Astrophysics and Cosmic Phenomena
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article
Field-Weighted Citation Impact
0.00

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Extreme PeV Accelerator Associated with GRS 1915+105

J. Chang, E. S. Chen, X. H. Cui, F. Aharonian et al.
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The Astrophysical Journal Letters
Astrophysics and Cosmic Phenomena
article

Extreme PeV Accelerator Associated with GRS 1915+105

J. Chang, E. S. Chen, X. H. Cui, F. Aharonian, D. Bastieri, T X Chen, S.Z. Chen, Q. B. Gou, XJ Huang, Jeffrey Blunier, S. C. Hu, H L He, M. H. Gu, Y. P. Guo, Y. Z. Fan, X. T. Feng, G. H. Chen, Y. W. Bao, X. B. Chen, S. H. Chen, H. L. Dai, W. Y. Cao, X. Y. He, M. M. Ge, N. Cheng, H. Feng, C. Huang, D. H. Huang, C. M. Cai, F. L. Guo, H. N. He, Z. G. Dai, J. Guo, S. H. Feng, J. H. Fan, T. T. Ge, Y. X. Bai, B. W. Hou, X. L. Guo, Y. X. Diao, A. V. Bukevich, H. B. Hu, S. W. Cui, Y. J. Bi, M. Y. Cui, J. H. Fang, J. Y. He, Q. H. Chen, X. J. Bi, Long Chen, B. Gao, Zhen Cao, Y. He, L. F. Chen, X. T. Huang, K. J. Guo, B. Z. Dai, A. J. Dong, R. P. Han, H. K. Chen, Q. Gao, Q. Y. Cheng, X. P. Chen, C. F. Feng, S. Chen, L. Feng, W. Bian, Y. Feng, J. Fang, Y. Y. Cai, X. Hou, M. L. Chen, C. Hou, Danzengluobu, Liang Chen, J. J. Huang, K. Fang, Y. Chen, M. M. Ge, R. P. Han, C. Ge, C. Hou, B. Z. Dai, H. H. He, G. H. Gong, Q. B. Gou, X. D. Duan, M. Hasan, M. Y. Cui, S. Gabici, J. Chang, X. L. Ji, A. Inventar, B. Gao, E. S. Chen, G. Giacinti, J. H. Fan
article en

Abstract

Abstract Microquasars, binary systems featuring relativistic jets, have emerged as sources for particle acceleration beyond PeV energies. We present a study of the broadband γ -ray emission from one of the most prominent Galactic microquasars, GRS 1915+105, based on data accumulated by LHAASO and Fermi Large Area Telescope over 4 and 17 yr, respectively. A joint analysis of LHAASO-WCDA and LHAASO-KM2A data reveals extended γ -ray emission whose centroid appears significantly shifted, by ∼0 . ° 13, from the binary system and its jets. The spectral energy distribution is well described by a curved spectrum with progressive steepening that can be described by a log-parabola function with no evidence for a sharp cutoff, consistent with parent particles reaching multi-PeV energies and an extreme acceleration efficiency approaching the limit set by the available potential drop across the source. Several features, most notably the shift of the emission and single power-law spectrum down to GeV band, favor radiation by cosmic rays accelerated in the source interacting with the dense ambient medium. Our spectral modeling implies that at least a few percent of the jet mechanical power is transferred to protons, whose maximum energy reaches beyond 5 PeV. These results strengthen the case for microquasars as exceptionally efficient accelerators in our Galaxy.

The Astrophysical Journal LettersVol. 1011(1)
University of Science and Technology of China (CN), Tibet University (CN), Shandong University (CN), Guizhou Normal University (CN), Sun Yat-sen University (CN), Chinese University of Hong Kong (HK), Shanghai Jiao Tong University (CN), Yunnan University (CN), Xiamen University (CN), Yerevan State University (AM), Chinese Academy of Sciences (CN), Université Paris Cité (FR), Guangzhou University (CN), Institute for Nuclear Research (RU), Max Planck Institute for Nuclear Physics (DE), University of Chinese Academy of Sciences (CN), Southwest Jiaotong University (CN), China Center of Advanced Science and Technology (CN), Henan Normal University (CN), Nanjing University (CN), University of Hong Kong (HK), Hebei Normal University (CN), Tsinghua University (CN)
National Natural Science Foundation of China, Chinese Academy of Sciences, Department of Science and Technology of Sichuan Province, National Key Research and Development Program of China, High Energy Physics
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Astrophysics and Cosmic Phenomena
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