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Binary Neutron Star Mergers as the Source of the Highest Energy Cosmic Rays
1Center for Cosmology and Particle Physics, Department of Physics, New York University, New York, New York 10003, USA.
Physical Review Letters
|March 14, 2025
Summary
Binary neutron star mergers may produce ultrahigh energy cosmic rays (UHECRs). This model explains the narrow energy range of UHECRs and predicts coincidences between high-energy neutrinos and gravitational waves.
Area of Science:
- Astrophysics
- Cosmic Ray Physics
- Gravitational Wave Astronomy
Background:
- Ultrahigh energy cosmic rays (UHECRs) exhibit a narrow rigidity range, a phenomenon not fully explained by current astrophysical models.
- Binary neutron star (BNS) mergers are powerful cosmic events with energetic jets, but their role in UHECR production is under-explored.
Purpose of the Study:
- To propose and investigate binary neutron star (BNS) mergers as the primary source of ultrahigh energy cosmic rays (UHECRs).
- To explain the observed narrow rigidity range of UHECRs within a BNS merger framework.
- To explore the potential for detecting coincident signals of high-energy neutrinos and gravitational waves from BNS mergers.
Main Methods:
- Modeling the jet production mechanism in BNS mergers, focusing on the role of the gravitationally driven dynamo.
- Simulating the acceleration and propagation of particles within BNS merger jets.
- Analyzing the expected spectrum and composition of cosmic rays, including r-process nuclei, originating from BNS mergers.
Main Results:
- The gravitationally driven dynamo in BNS mergers naturally produces jets with nearly identical properties, explaining the narrow rigidity range of UHECRs.
- UHECRs with energies exceeding 100 EeV can be attributed to r-process nuclei ejected during BNS mergers.
- The model predicts observable coincidences between neutrinos with energies above 10 PeV and gravitational wave events from BNS mergers.
Conclusions:
- Binary neutron star mergers provide a viable and consistent explanation for the origin of ultrahigh energy cosmic rays.
- This scenario eliminates the need for exotic or unknown sources to explain the highest energy cosmic rays observed.
- The predicted coincident detection of high-energy neutrinos and gravitational waves offers a unique observational test for this BNS merger UHECR production mechanism.
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