Locating ergostar models in parameter space

Abstract

Recently, we have shown that dynamically stable ergostar solutions (equilibrium neutron stars that contain an ergoregion) with a compressible and causal equation of state exist [A. Tsokaros, M. Ruiz, L. Sun, S. L. Shapiro, and K. Uryū, Phys. Rev. Lett. 123, 231103 (2019)]. These stars are hypermassive, differentially rotating, and highly compact. In this work, we make a systematic study of equilibrium models in order to locate the position of ergostars in parameter space. We adopt four equations of state that differ in the matching density of a maximally stiff core. By constructing a large number of models both with uniform and differential rotation of different degrees, we identify the parameters for which ergostars appear. We find that the most favorable conditions for the appearance of dynamically stable ergostars are a significant finite density close to the surface of the star (i.e., similar to self-bound quark stars) and a small degree of differential rotation.

arXiv comment8 pages, 3 figures. Matches published version

References in corpus (26)

• GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral
• A unified equation of state of dense matter and neutron star structure
• INTEGRAL Detection of the First Prompt Gamma-Ray Signal Coincident with the Gravitational Wave Event GW170817
• Constraints on a phenomenologically parameterized neutron-star equation of state
• The Equation of State of Hot, Dense Matter and Neutron Stars
• Comparing Models of Rapidly Rotating Relativistic Stars Constructed by Two Numerical Methods
• On the Maximum Mass of Differentially Rotating Neutron Stars
• Binary neutron star mergers: a jet engine for short gamma-ray bursts
• Observations of the Blandford-Znajek and the MHD Penrose processes in computer simulations of black hole magnetospheres
• The bar-mode instability in differentially rotating neutron stars: Simulations in full general relativity
• Relativistic simulations of black hole-neutron star coalescence: the jet emerges
• Differential Rotation in Neutron Stars: Magnetic Braking and Viscous Damping
• Collapse of magnetized hypermassive neutron stars in general relativity
• The Influence of Thermal Pressure on Equilibrium Models of Hypermassive Neutron Star Merger Remnants
• A quasi-radial stability criterion for rotating relativistic stars
• Highly accurate calculation of rotating neutron stars
• On the stability and maximum mass of differentially rotating relativistic stars
• Semi-analytic derivation of the threshold mass for prompt collapse in binary neutron star mergers
• On the Solution Space of Differentially Rotating Neutron Stars in General Relativity
• Jet launching from binary black hole-neutron star mergers: Dependence on black hole spin, binary mass ratio and magnetic field orientation
• Modeling differential rotations of compact stars in equilibriums
• A proof of Friedman's ergosphere instability for scalar waves
• The role of the ergosphere in the Blandford-Znajek process
• Great Impostors: Extremely Compact, Merging Binary Neutron Stars in the Mass Gap Posing as Binary Black Holes
• On the dynamical stability of quasi-toroidal differentially rotating neutron stars
• Dynamically stable ergostars exist: General relativistic models and simulations

Cited by in corpus (8)

• Multimessenger Binary Mergers Containing Neutron Stars: Gravitational Waves, Jets, and $\mathbf{\gamma }$-Ray Bursts
• Models of binary neutron star remnants with tabulated equations of state
• Jetlike structures in low-mass binary neutron star merger remnants
• Accretion onto black holes inside neutron stars with piecewise-polytropic equations of state: analytic and numerical treatments
• Magnetic Ergostars, Jet Formation and Gamma-Ray Bursts: Ergoregions versus Horizons
• Ergoregion instability in bosonic stars: scalar mode structure, universality, and weakly nonlinear effects
• Energy bounds and ergoregion instability in Einstein-Maxwell-Scalar field models
• Nonlinear evolution of the ergoregion instability: Turbulence, bursts of radiation, and black hole formation