Hyperons in Neutron Stars across the observed mass range: Insights from realistic $\Lambda$-N and $\Lambda$-$\Lambda$ interactions within a Microscopic Framework

Abstract

We investigate the equation of state (EOS) and macroscopic properties of neutron stars (NSs) and hyperonic stars within the framework of the lowest order constrained variational (LOCV) method, extended to include interacting $\Lambda$ hyperons. The nucleon-nucleon interaction is modeled using the AV18 potential supplemented by Urbana three-body forces, while $\Lambda N$ and $\Lambda \Lambda$ interactions are described by realistic spin- and parity-dependent potentials fitted to hypernuclear data. Cold, charge-neutral, and $\beta$-equilibrated matter composed of neutrons, protons, electrons, muons, and $\Lambda$ hyperons is considered. We compute particle fractions, chemical potentials, the EOS, speed of sound, tidal deformability, and stellar structure by solving the Tolman-Oppenheimer-Volkoff equations, and compare our results with recent NICER and gravitational-wave observations. The inclusion of $\Lambda$ hyperons leads to EOS softening, reducing the maximum NS mass from $2.34M_{\odot }$ to $2.07M_{\odot }$, while keeping it consistent with the $2M_{\odot }$ mass constraint. At $1.4M_{\odot }$, the model satisfies observational limits on radius and tidal deformability, with the $\Lambda$ onset occurring below this mass. Comparison with other microscopic and relativistic mean-field models shows that our EOS remains consistent with the allowed pressure-energy density range, while also permitting even canonical-mass NSs of about $1.4M_{\odot }$ to accommodate hyperons. These results suggest that hyperons can appear in NSs across the observed mass range without violating current astrophysical constraints, and that the extended LOCV method provides a consistent, microscopic approach to modeling dense hypernuclear matter.

Published in Astrophysical Journal 997 (2026) 26

References in corpus (21)

• A Massive Pulsar in a Compact Relativistic Binary
• PSR J0030+0451 Mass and Radius from NICER Data and Implications for the Properties of Neutron Star Matter
• Refined Mass and Geometric Measurements of the High-Mass PSR J0740+6620
• Hyperon Puzzle: Hints from Quantum Monte Carlo Calculations
• A NICER View of the Nearest and Brightest Millisecond Pulsar: PSR J0437$\unicode{x2013}$4715
• Neutron Stars and the Nuclear Equation of State
• An updated mass-radius analysis of the 2017-2018 NICER data set of PSR J0030+0451
• Estimation of the effect of hyperonic three-body forces on the maximum mass of neutron stars
• Hyperon mixing and universal many-body repulsion in neutron stars
• Heavy Baryons in Compact Stars
• A NICER view of the 1.4 solar-mass edge-on pulsar PSR J0614-3329
• Hyperon-nucleon interaction in chiral effective field theory at next-to-next-to-leading order
• Constraining a relativistic mean field model using neutron star mass-radius measurements II: Hyperonic models
• $\Lambda$ hypernuclear potentials beyond linear density dependence
• The impact of hyperons on neutron star mergers: gravitational waves, mass ejection and black hole formation
• Impact of QCD sum rules coupling constants on neutron stars structure
• Hybrid stars within the framework of the Sigma-Omega-Rho model combined with the MIT and NJL models
• Impact of $\Xi$-Hypernuclear Constraints on Relativistic Equation of State and Properties of Hyperon Stars
• Compatibility of recent $\Xi$-nuclear bound state signals
• $\Xi$-nuclear constraints from ${\Xi }^{-}$ emulsion capture events
• $\Lambda NN$ input to neutron stars from hypernuclear data

Cited by in corpus (2)

• Probing Strange Dark Matter through $f$-mode Oscillations of Neutron Stars with Hyperons and Quark Matter
• Exploring Hyperon Skyrme Forces in Multi-$\Lambda$ Hypernuclei and Neutron Star Matter