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.
Related
- Solar extreme-ultraviolet waves and other associated solar activities
- Accelerator neutrinos as a probe of in-medium hyperon potentials
- A Galactic microblazar as a potential accelerator of ultra-high-energy particles
- An ALMA view of the Jet-Arc CO clouds toward the TeV γ-ray source HESS J1023-575 and Westerlund 2; Evidence for the footprints of microquasar jets, the very powerful cosmic-ray accelerator in the Galactic disk
- XMM-Newton observations of the highest field polar AR UMa. An extreme case of soft-blobby accretion
BibTeX
@article{cao2026extreme,
title = {{Extreme PeV Accelerator Associated with GRS 1915+105}},
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. Butkevich and C. M. 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 L. X. Dai and Z. G. Dai and Danzengluobu and Y. X. Diao and A. J. Dong and X. D. 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},
journal = {The Astrophysical Journal Letters},
year = {2026},
month = oct,
doi = {10.3847/2041-8213/aeaa27},
url = {https://iopscience.iop.org/article/10.3847/2041-8213/aeaa27},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Extreme PeV Accelerator Associated with GRS 1915+105
AU - Zhen Cao
AU - F. Aharonian
AU - Y. X. Bai
AU - Y. W. Bao
AU - D. Bastieri
AU - X. J. Bi
AU - Y. J. Bi
AU - W. Bian
AU - J. Blunier
AU - A. V. Butkevich
AU - C. M. Cai
AU - W. Y. Cao
AU - Zhe Cao
AU - J. Chang
AU - J. F. Chang
AU - E. S. Chen
AU - G. H. Chen
AU - H. K. Chen
AU - L. F. Chen
AU - Liang Chen
AU - Long Chen
AU - M. J. Chen
AU - M. L. Chen
AU - Q. H. Chen
AU - S. Chen
AU - S. H. Chen
AU - S. Z. Chen
AU - T. L. Chen
AU - X. B. Chen
AU - X. J. Chen
AU - X. P. Chen
AU - Y. Chen
AU - N. Cheng
AU - Q. Y. Cheng
AU - Y. D. Cheng
AU - M. Y. Cui
AU - S. W. Cui
AU - X. H. Cui
AU - Y. D. Cui
AU - B. Z. Dai
AU - H. L. Dai
AU - L. X. Dai
AU - Z. G. Dai
AU - Danzengluobu
AU - Y. X. Diao
AU - A. J. Dong
AU - X. D. Duan
AU - J. H. Fan
AU - Y. Z. Fan
AU - J. Fang
AU - J. H. Fang
AU - K. Fang
AU - C. F. Feng
AU - H. Feng
AU - L. Feng
AU - S. H. Feng
AU - X. T. Feng
AU - Y. Feng
AU - Y. L. Feng
AU - S. Gabici
PY - 2026
DA - 2026/10/29
JO - The Astrophysical Journal Letters
DO - 10.3847/2041-8213/aeaa27
UR - https://iopscience.iop.org/article/10.3847/2041-8213/aeaa27
AB - 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.
SN - 2041-8213
SN - 2041-8205
ER -