Influence of muons, pions, and trapped neutrinos on neutron star mergers
Abstract
The merger of two neutron stars probes dense matter in a hot, neutrino-trapped regime. In this work, we investigate how fully accounting for pions (𝜋), muons (𝜇), and muon-type neutrinos (𝜈𝜇) in the trapped regime may affect the outcome of the merger. By performing fully general-relativistic hydrodynamics simulations of merging neutron stars with equations of state to which we systematically add those different particle species, we aim to provide a detailed assessment of the impact of muons and pions on the merger and postmerger phases. In particular, we investigate the merger thermodynamics, mass ejection, and gravitational wave emission. Our findings are consistent with previous expectations, that the inclusion of such microphysical degrees of freedom and finite temperature corrections leads to frequency shifts on the order of 100–200 Hz in the postmerger gravitational wave signal, relative to a fiducial cold nucleonic equation-of-state model.
Copyright and License
© 2025 American Physical Society.
Acknowledgement
The authors are grateful for helpful conversations with Eleonora Loffredo, Ninoy Rahman, and Javier Roulet. Analysis for this work was done using matplotlib [150], numpy [151], scipy [152], and kuibit [153]. M. A. P. was supported by the Sherman Fairchild Foundation, NSF Grant No. PHY-2309211, No. PHY-2309231, and No. OAC-2209656 at Caltech. E. R. M. acknowledges support by the National Science Foundation under Grants No. PHY-2309210 and No. OAC-2103680. This work mainly used Delta at the National Center for Supercomputing Applications (NCSA) through allocation No. PHY210074 from the Advanced Cyberinfrastructure Coordination Ecosystem: Services & Support (ACCESS) program, which is supported by National Science Foundation Grants No. 2138259, No. 2138286, No. 2138307, No. 2137603, and No. 2138296. Additional simulations were performed on the NSF Frontera supercomputer under Grant No. AST21006.
Data Availability
No data were created or analyzed outside that presented in this manuscript.
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Additional details
- Sherman Fairchild Foundation
- National Science Foundation
- PHY-2309211
- National Science Foundation
- PHY-2309231
- National Science Foundation
- OAC-2209656
- National Science Foundation
- PHY-2309210
- National Science Foundation
- OAC-2103680
- National Science Foundation
- PHY210074
- National Science Foundation
- OAC-2138259
- National Science Foundation
- OAC-2138286
- National Science Foundation
- OAC-2138307
- National Science Foundation
- OAC-2137603
- National Science Foundation
- OAC-2138296
- National Science Foundation
- AST21006
- Accepted
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2025-01-15Accepted
- Caltech groups
- Astronomy Department, TAPIR, Walter Burke Institute for Theoretical Physics
- Publication Status
- Published