Isospin equilibration in neutron star mergers

Journal Article · 07 May 2024 · Physical Review. C

DOI: https://doi.org/10.1103/physrevc.109.055803 · OSTI ID:2349120

Alford, Mark G.  ^[1]; Haber, Alexander  ^[2]; Zhang, Ziyuan  ^[2]

---

1. Washington University in St. Louis, MO (United States); Washington University in St. Louis
2. Washington University in St. Louis, MO (United States)

We analyze the isospin equilibration properties of neutrinoless nuclear (npe) matter in the temperature and density range that is relevant to neutron star mergers. Our analysis incorporates neutrino-transparency corrections to the isospin (“beta”) equilibrium condition which become noticeable at T ≳ 1 MeV. We find that the isospin relaxation rate rises rapidly as temperature rises, and at T ≈ 5 MeV it is comparable to the timescale of the density oscillations that occur immediately after the merger. This produces a resonant peak in the bulk viscosity at T ≈ 5 MeV, which causes density oscillations to be damped on the timescale of the merger. Furthermore, our calculations suggest that isospin relaxation dynamics may also be relevant when neutrinos are treated more accurately via neutrino transport schemes.

• Research Organization: Washington University in St. Louis, MO (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Nuclear Physics (NP)
• Grant/Contract Number: FG02-05ER41375
• OSTI ID: 2349120
• Alternate ID(s): OSTI ID: 2350832; OSTI ID: 2356876; OSTI ID: 2438412
• Journal Information: Physical Review. C, Journal Name: Physical Review. C Journal Issue: 5 Vol. 109; ISSN 2469-9985
• Publisher: American Physical Society (APS)Copyright Statement
• Country of Publication: United States
• Language: English