Roles of crust and core in the tidal deformability of neutron stars

Abstract

With the recent measurement of GW170817 providing constraints on the tidal deformability of a neutron star, it is very important to understand what features of the equation of state have the biggest effect on it. We therefore study the contribution of the crust to the tidal deformability and the moment of inertia of a neutron star for a variety of well-known equations of state. It is found that the contributions to these quantities from the low density crust are typically quite small and as a result the determination of the tidal deformability provides an important constraint on the equation of state of dense matter.

Neutron-star tidal deformability and equation-of-state constraints

“…The neutron star pressure at twice saturation was constrained to 3.5 +2.7 −1.7 × 10 34 dyn/cm 2 , which was shown to be consistent with low density results from terrestrial heavy-ion collision experiments [15,18] in [214]. The treatment of the neutron star crust [215] in the polytropic and spectral representations affects Λ to less than 1% [216,217], and similarly for the radius. For GW170817 and using the spectral representation, the crust model affects the radius to 100 − 200m [218], which is smaller than the statistical error of 2 − 3km at the 90% level.…”

Role of the crust in the tidal deformability of a neutron star within a unified treatment of dense matter

“…12 and previously noticed in Refs. [4][5][6]. The impact of the crust on Λ is found to be significantly weaker than that previously reported in Ref.…”

“…Although the crust leads to a strong reduction of k 2 , its effect on the tidal deformability parameter Λ is mitigated by the increase in the radius R, as previously noticed in Refs. [4,5]. However, contrary to Ref.…”

“…The importance of the crustal regions for the determination of the Love number k 2 and the tidal deformability Λ of a NS has been recently investigated [4][5][6]. In Ref.…”

“…All of these studies concluded that k 2 is very sensitive to the crustal EoS unlike the observable tidal deformability parameter Λ. However, these studies lead to widely different estimates for the contribution of the crust on Λ, ranging from 0.1% [4] to about 11% [5] for a 1.4M NS.…”