Speed of sound constraints on maximally rotating neutron stars

Abstract

The observation of maximally rotating neutron stars (in comparison to nonrotating ones) may provide more information on the behavior of nuclear matter at high densities. We provide a theoretical treatment concerning the effects of the upper bound of the sound speed in dense matter on the bulk properties of maximally rotating (at mass-shedding limit) neutron stars. In particular, we consider two upper bounds for the speed of sound, $v_s=c$ and $v_s=c/\sqrt{3}$, and the one provided by the relativistic kinetic theory. We investigate to what extent the possible predicted (from various theories and conjectures) upper bounds on the speed of sound constrain the ones of various key quantities, including the maximum mass and the corresponding radius, Keplerian frequency, Kerr parameter and moment of inertia. We mainly focus on the lower proposed limit, $v_s=c/\sqrt{3}$, and we explore in which mass region a rotating neutron star collapses to a black hole. In any case, useful relations of the mentioned bulk properties with the transition density are derived and compared with the corresponding nonrotating cases. We concluded that the proposed limit $v_s=c/\sqrt{3}$ leads to dramatic decrease on the values of the maximum mass, Kerr parameter and moment of inertia preventing a neutron star to reach values which derived with the consideration of realistic equations of state or from other constraints. Possible measurements of the Kerr parameter and moment of inertia would shed light on these issues and help to reveal the speed of sound bound in dense matter.

arXiv commentv1: 8 pages, 10 figures, 2 tables. v2: 10 pages, 15 figures, 3 tables; sections, tables, figures and references had been added. v3: 12 pages, 10 figures, 5 tables; accepted for publication in Phy. Rev. D

References in corpus (30)

• GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral
• A Massive Pulsar in a Compact Relativistic Binary
• The equation of state for nucleon matter and neutron star structure
• Relativistic Shapiro delay measurements of an extremely massive millisecond pulsar
• The NANOGrav 11-year Data Set: High-precision timing of 45 Millisecond Pulsars
• Rotating Stars in Relativity
• Comparing Models of Rapidly Rotating Relativistic Stars Constructed by Two Numerical Methods
• Black Holes
• Generic conditions for stable hybrid stars
• The Maximum Mass of a Neutron Star
• Constraining the speed of sound inside neutron stars with chiral effective field theory interactions and observations
• Peering into the dark side: magnesium lines establish a massive neutron star in PSR J2215+5135
• Sound velocity bound and neutron stars
• Evidence for a maximum mass cut-off in the neutron star mass distribution and constraints on the equation of state
• Gravitational waves from neutron star mergers and their relation to the nuclear equation of state
• Rotating Stars in Relativity
• Upper Limit Set by Causality on the Rotation and Mass of Uniformly Rotating Relativistic Stars
• Keplerian frequency of uniformly rotating neutron stars and quark stars
• Fast Rotating Neutron Stars with Realistic Nuclear Matter Equation of State
• Confronting gravitational-wave observations with modern nuclear physics constraints
• The spin parameter of uniformly rotating compact stars
• On the Maximum Mass of Neutron Stars
• Bounds on the speed of sound in dense matter, and neutron star structure
• Effects of the equation of state on the bulk properties of maximally-rotating neutron stars
• Upper limit set by causality on the tidal deformability of a neutron star
• Trace of the energy-momentum tensor and macroscopic properties of neutron stars
• Sound velocity and tidal deformability in compact stars
• Maximally incompressible neutron star matter
• Constraints on the equation of state from the stability condition of neutron stars
• I-Love-Q to the extreme

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• Speed of sound constraints from tidal deformability of neutron stars
• Probing the nuclear equation of state from the existence of a $\sim 2.6M_{\odot }$ neutron star: the GW190814 puzzle
• Twin stars as probes of the nuclear equation of state: effects of rotation through the PSR J0952-0607 pulsar and constraints via the tidal deformability from the GW170817 event
• On the moment of inertia of PSR J0737-3039 A from LIGO/Virgo and NICER
• Insights on the peak in the speed of sound of ultradense matter
• $2.6M_{\odot }$ Compact Object and Neutron Stars within Eddington-Inspired Born-Infeld Theory of Gravity
• Causality violation and the speed of sound of hot and dense quark matter in the Nambu--Jona-Lasinio model
• Speed of Sound for Hadronic and Quark Phases in a Magnetic Field
• Speed of sound bounds and first-order phase transitions in compact stars
• Is the central compact object in HESS J1731-347 a hybrid star with a quark core? An analysis with the constant speed of sound parametrization
• Hyperons, deconfinement and the speed of sound in neutron stars
• Neutron Stars and Gravitational Waves: the Key Role of Nuclear Equation of State
• General gravitational properties of neutron stars: curvature invariants, binding energy, and trace anomaly