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

Abstract

The role of the crust on the tidal deformability of a cold nonaccreted neutron star is studied using the recent unified equation of state BSk24. This equation of state, which is based on the nuclear-energy density functional theory, provides a thermodynamically consistent description of all stellar regions. Results obtained with this equation of state are compared to those calculated for a putative neutron star made entirely of homogeneous matter. The presence of the crustal layers is thus found to significantly reduce the Love number k 2 , especially for low-mass stars. However, this reduction mainly arises from the increase in the stellar radius almost independently of the equation of state. This allows for a simple analytic estimate of k 2 for realistic neutron stars using the equation of state of homogeneous matter only.

Role of dense matter in tidal deformations of inspiralling neutron stars and in gravitational waveforms with unified equations of state

“…[42] using a few EoSs based on relativistic mean-field models. However, the adopted EoSs in the outer and inner regions of the crust were not specified although the crust has a strong impact on the values of the Love numbers [39]. The ad hoc matching of different EoSs may also lead to uncertainties as large as 20% for one-solar mass NSs [57].…”

“…Following our previous study [39], we have pursued our analysis of the role of the crust in the tidal deformability of a NS. To this end, we have compared results obtained using the unified EoS BSk24 to those obtained considering a putative NS made entirely of homogeneous matter (see Ref.…”

“…To this end, we have compared results obtained using the unified EoS BSk24 to those obtained considering a putative NS made entirely of homogeneous matter (see Ref. [39]). Although the existence of a mantle of nuclear pastas beneath the crust was not considered in Ref.…”

“…[37]. Although the errors incurred by the neglect of j 2 amount to a few percent, these deviations turn out to be much larger than those due to the crust [38][39][40]. More importantly, they will be potentially observable with third-generation gravitational-wave detectors, thus offering new possibilities to probe the interior of NSs [41].…”

Systematic analysis of inner crust composition using the extended Thomas-Fermi approximation with pairing correlations

“…Although the crust only accounts for a small fraction of the mass of the NS, it plays a major role in a variety of astrophysical phenomena, including the r-process [4], short gamma-ray burst precursors caused by resonant shattering [5], soft gamma-ray repeater giant flares [6,7], and thermal relaxation in soft x-ray transients. The equation of state (EoS) of the crust is also believed to influence many properties of NS, such as the moment of inertia [8] which influences pulsar glitches, transport phenomena within the star [9][10][11], the relation between the radius and tidal deformability in low-mass NS [12], and the value of the second Love number, k 2 [13,14]. Therefore it is crucial to have a reliable model of the crust of a NS, in order to achieve accurate descriptions of these phenomena.…”