What if the neutron star maximum mass is beyond ∼2.3 M⊙?. Issue 3 (12th October 2020)

• Record Type: Journal Article
• Authors: Wu, X H; Du, S; Xu, R X
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 499:Issue 3(2020)
• Page Start: 4526
• Page End: 4533
• Publication Date: 2020-10-12
• Subjects: equation of state -- stars: neutron -- pulsars: general; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/staa3145
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: By assuming the formation of a black hole soon after the merger event of GW170817, the maximum mass of non-rotating stable neutron star, M TOV ≃ 2.3 M⊙, is proposed by numerical relativity, but there is no solid evidence to rule out M TOV > 2.3 M⊙ from the point of both microphysical and astrophysical views. It is naturally expected that the equation of state (EOS) would become stiffer beyond a specific density to explain massive pulsars. We consider the possibility of EOSs with M TOV > 2.3 M⊙, investigating the stiffness and the transition density in a polytropic model, for two kinds of neutron stars (i.e. gravity-bound and strong-bound stars on surface). Only two parameters are input in both cases: (ρt, γ) for gravity-bound neutron stars, while (ρs, γ) for strong-bound strange stars, with ρt the transition density, ρs the surface density, and γ the polytropic exponent. In the matter of M TOV > 2.3 M⊙ for the maximum mass and 70 ≤ Λ1.4 ≤ 580 for the tidal deformability, it is found that the smallest ρt and γ should be ∼0.50 ρ0 and ∼2.65 for neutron stars, respectively, whereas for strange star, we have γ > 1.40 if ρs > 1.0 ρ0 (ρ0 is the nuclear saturation density). These parametric results could guide further research of the real EOS with any foundation of microphysics if a pulsar mass higher than 2.3 M⊙ is measured in the future, especially for an essential comparison of allowed parameter space between gravity-bound and strong-bound compact stars.