Delta baryons and diquark formation in the cores of neutron stars

Abstract

We investigate the hadron-quark phase transition in cold neutron stars in light of (i) the observed limits on the maximum-mass of heavy pulsars, (ii) constraints on the tidal properties inferred from the gravitational waves emitted in binary neutron-star mergers, and (iii) mass and radius constraints derived from the observation of hot spots on neutron star observed with NICER. Special attention is directed to the possible presence of $\Delta (1232)$ baryons in neutron star matter. Our results indicate that this particle could make up a large fraction of the baryons in neutron stars and thus have a significant effect on the properties of such objects, particularly on their radii. This is partially caused by the low density appearance of $\Delta$s for a wide range of theoretically defensible sets of meson-hyperon, SU(3) ESC08 model, and meson-$\Delta$ coupling constants. The transition of hadronic matter to quark matter, treated in the 2SC+s condensation phase, is found to occur only in neutron stars very close to the mass peak. Nevertheless, quark matter may still constitute an appreciable fraction of the stars' total matter if the phase transition is treated as Maxwell-like (sharp), in which case the neutron stars located beyond the gravitational mass peak would remain stable against gravitational collapse. In this case, the instability against gravitational collapse is shifted to a new (terminal) mass different from the maximum-mass of the stellar sequence, giving rise to stable compact objects with the same gravitational masses as those of the neutron stars on the traditional branch, but whose radii are smaller by up to 1 km. All models for the equation of state of our study fall comfortably within the bound established very recently by Annala {\it et al.} (Nature Physics, 2020)

18 Pages, 13 Figures, Accepted for publication in Physical Review D, in production

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• Extreme Matter meets Extreme Gravity: Ultra-heavy neutron stars with crossovers and first-order phase transitions
• Relativistic hybrid stars in light of the NICER PSR J0740+6620 radius measurement
• The slope, the hill, the drop, and the swoosh: Learning about the nuclear matter equation of state from the binary Love relations
• Rapidly rotating $\Delta$-resonance-admixed hypernuclear compact stars
• Delta Baryons in Neutron-Star Matter under Strong Magnetic Fields
• Insights on the peak in the speed of sound of ultradense matter
• Hybrid stars with sequential phase transitions: the emergence of the g${}_2$ mode
• Hybrid star models in the light of new multi-messenger data
• Chiral symmetry restoration and the $\Delta$ matter formation in neutron stars
• Relativistic hybrid stars with sequential first-order phase transitions in light of multimessenger constraints
• On the Speed of Sound in Hyperonic Stars
• Universal relations for compact stars with heavy baryons
• Delta baryons in neutron stars
• Could a slow stable hybrid star explain the central compact object in HESS~J1731-347?
• Radial Oscillations in Neutron Stars with Delta Baryons
• Oscillating magnetised hybrid stars under the magnifying glass of multi-messenger observations
• Asteroseismology using quadrupolar f-modes revisited: breaking of universal relationships in the slow hadron-quark conversion scenario
• Exploring the effects of Delta Baryons in magnetars
• Strong-interaction matter under extreme conditions from chiral quark models with nonlocal separable interactions
• Breaking of universal relationships of axial wI-modes in hybrid stars: rapid and slow hadron-quark conversion scenarios
• Speed of Sound for Hadronic and Quark Phases in a Magnetic Field
• Hybrid stars with color superconducting cores in an extended FCM model
• Neural Simulation-Based Inference of the Neutron Star Equation of State directly from Telescope Spectra
• Novel Scalings of Neutron Star Properties from Analyzing Dimensionless Tolman--Oppenheimer--Volkoff Equations
• Massive relativistic compact stars from SU(3) symmetric quark models
• (Anti)kaon condensation in strongly magnetized dense matter
• Exploring Baryon Resonances with Transition Generalized Parton Distributions: Status and Perspectives
• Probing the impact of Delta-Baryons on Nuclear Matter and Non-Radial Oscillations in Neutron Stars
• Strong Gravity Extruding Peaks in Speed of Sound Profiles of Massive Neutron Stars
• Strangeness thermodynamic instabilities in hot and dense nuclear matter
• Towards a unified hadron-quark equation of state for neutron stars within the relativistic mean-field model
• Non-Radial Oscillation Modes in Hybrid Stars with Hyperons and Delta Baryons
• Investigating the Impact of Higher-Order Phase Transitions in Binary Neutron-Star Mergers
• Consistent crust-core interpolation and its effect on non-radial neutron star oscillations
• How Neutron Star Observations Point Towards Exotic Matter: Existing Explanations and a Prospective Proposal
• A study of the elastic $\pi N$ scattering at finite baryon density
• Classification of $g$-modes for neutron stars with a strong transition: Novel universal relation including slow stable hybrid stars
• On the Destabilization of High-Mass Neutron Stars by the Emergence of $d^{\ast }$-Hexaquarks
• Baryons in the Nambu Jona-Lasinio models
• Recurring region for neutron-star observables