Millisecond radio pulsars with known masses: Parameter values and equation of state models

Abstract

The recent fast growth of a population of millisecond pulsars with precisely measured mass provides an excellent opportunity to characterize these compact stars at an unprecedented level. This is because the stellar parameter values can be accurately computed for known mass and spin rate and an assumed equation of state (EoS) model. For each of the 16 such pulsars and for a set of EoS models from nucleonic, hyperonic, strange quark matter and hybrid classes, we numerically compute fast spinning stable stellar parameter values considering the full effect of general relativity. This first detailed catalogue of the computed parameter values of observed millisecond pulsars provides a testbed to probe the physics of compact stars, including their formation, evolution and EoS. We estimate uncertainties on these computed values from the uncertainty of the measured mass, which could be useful to quantitatively constrain EoS models. We note that the largest value of the central density ρ c in our catalogue is ∼ 5.8 times the nuclear saturation density ρ sat , which is much less than the expected maximum value 13ρ sat . We argue that the ρ c -values of at most a small fraction of compact stars could be much larger than 5.8ρ sat . Besides, we find that the constraints on EoS models from accurate radius measurements could be significantly biased for some of our pulsars, if stellar spinning configurations are not used to compute the theoretical radius values.

Neutron star equation of state and GW170817

“…These values of moments of inertia are consistent with the theoretically predicted values of Ref. [34]. As we know the moment of inertia and mass of each component, it is possible to estimate the radius of the corresponding component.…”

Structural Properties of Rotating Hybrid Compact Stars with Color-Flavour-Locked Quarks Matter core and its Tidal Deformability

“…The evolutionary sequences of the pulsars, theoretical limits of the radii and the gravitational mass of these pulsars have been computed by using NHymQ4 equation of state of hybrid star. For slow rotating hybrid star of gravitational maximum mass around 1.4M ⊙ , the limits of the radii varies as 13.71km≤R eq ≤14.10km which is very close with the recently extracted bounds on radii of the compact stars [6,81]. Whereas for the spinning hybrid star with gravitational mass around 2.0M ⊙ , we predict the limits of radii as, 12.85km≤R eq ≤13.50km.…”

Last stable orbit around rapidly rotating neutron stars

“…where j ≡ cJ/(GM 2 ). This relation has been shown to be very accurate also in the description of the binding energy of other nuclear EOS models including hyperonic and hybrid ones [15]. The total energy released in an accretion process is given by the amount of gravitational energy gained by the material in its way to the NS surface and that is not arXiv:1612.02207v3 [astro-ph.HE] 14 Jun 2017 spent in increasing the gravitational binding energy of the NS, namely (see, e.g., [11,16]):…”