Neutron star crust in Voigt approximation II: general formula for electron screening correction for effective shear modulus

Chugunov, A. I.

doi:10.1093/mnras/stac2157

Cited by 3 publications

(2 citation statements)

References 60 publications

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“…For nuclei crystallized into a body-centered cubic lattice, the Madelung constant is given by C M = −0.895929255682 [29]. Treating the crust as a polycrystal at the scales of interest here, the effective shear modulus is given by [30]…”

Section: Equation Of State Of Strange Dwarfs 21 Hadronic Envelopementioning

confidence: 99%

Role of Quark Matter and Color Superconductivity in the Structure and Tidal Deformability of Strange Dwarfs

Perot,

Chamel

2023

Universe

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In 1995, Glendenning, Kettner and Weber postulated the existence of a new class of compact stars resembling white dwarfs but containing a small strange quark-matter core surrounded by hadronic layers attaining much higher densities than those found in white dwarfs. In our previous study, we have shown that it could be possible to unmask these so-called strange dwarfs through gravitational-wave observations with future space-based detectors such as the Laser Interferometer Space Antenna. We calculated more realistic equations of state for the hadronic envelope, but the quark core was treated using the simplest MIT bag model. In this paper, we investigate more closely the role of the possibly solid core in the structure and the tidal deformability of strange dwarfs in the full general relativistic framework by considering different models of strange quark matter in the crystalline color -superconducting phase. We find that the effect of the extreme rigidity of the elastic core on the tidal deformability is almost completely canceled by the surrounding hadronic layers. However, in all cases, the tidal deformability of strange dwarfs remains sufficiently lower than that of white dwarfs, to be potentially observable with gravitational waves despite the uncertainties in the strange quark-matter equation of state.

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Section: Equation Of State Of Strange Dwarfs 21 Hadronic Envelopementioning

confidence: 99%

Role of Quark Matter and Color Superconductivity in the Structure and Tidal Deformability of Strange Dwarfs

Perot,

Chamel

2023

Universe

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“…At the scales of interest for the global description of tidal deformations, we assume that each stellar matter element consists of an isotropic polycrystalline solid. The elastic properties are thus characterized by a single parameter, the effective shear modulus given by [45][46][47]…”

Section: Equation Of State Of Strange Dwarfs a Layers Of Hadronic Mattermentioning

confidence: 99%

Unmasking strange dwarfs with gravitational-wave observations

2023

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The advent of space-based gravitational-wave detectors like the Laser Interferometer Space Antenna will allow us to observe signals, most of which are expected to be emitted by white-dwarf binaries. Among these systems another kind of compact objects could be hidden, postulated by Glendenning, Kettner, and Weber in 1995, containing a small core made of strange quark matter surrounded by layers of hadronic matter reaching densities much higher than in white dwarfs. These so-called strange dwarfs cannot be easily distinguished from white dwarfs through electromagnetic observations alone; their outermost envelopes are expected to have the same composition and their radii are quite similar (except for low masses). However, future measurements of the tidal deformability through gravitational-wave observations could provide a new way to reveal their existence. In this paper, we revisit the structure and the tidal deformability of strange dwarfs in full general relativity taking into account the possible crystallization of their envelope. Unlike most previous studies, we do not describe the hadronic layers using the equation of state of Baym, Pethick, and Sutherland, which was originally designed for the outer crust of a neutron star. The conditions leading to such heavy elements in gravitational-core collapse supernova explosions are not expected to be met during the stellar evolution leading to the formation of strange dwarfs. Instead, we consider the same light elements as found in white dwarfs but we take into account electron captures by nuclei and possibly pycnonuclear fusions that may be triggered by compression. We find that the radius of strange dwarfs is systematically smaller than that of their white dwarf relatives. These deviations can be large for very low-mass stars but mostly lie within the current observational uncertainties for typical white dwarf masses. On the other hand, the observable tidal deformability coefficient Λ 2 is strongly reduced in comparison to white dwarfs and the deviation will be potentially measurable by future space-based gravitational-wave detectors.

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Neutron star inner crust: reduction of shear modulus by nuclei finite size effect

Chugunov

2022

Monthly Notices of the Royal Astronomical Society

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The elasticity of neutron star crust is important for adequate interpretation of observations. To describe elastic properties one should rely on theoretical models. The most widely used is Coulomb crystal model (system of point-like charges on neutralizing uniform background), in some works it is corrected for electron screening. These models neglect finite size of nuclei. This approximation is well justified except for the innermost crustal layers, where nuclei size becomes comparable with the inter-nuclear spacing. Still, even in those dense layers it seems reasonable to apply the Coulomb crystal result, if one assumes that nuclei are spherically symmetric: Coulomb interaction between them should be the same as interaction between point-like charges. This argument is indeed correct, however, as we point here, shear of crustal lattice generates (microscopic) quadrupole electrostatic potential in a vicinity of lattice cites, which induces deformation on the nuclei. We analyze this problem analytically within compressible liquid drop model. In particular, for ground state crust composition the effective shear modulus is reduced for a factor of 1 − u5/3/(2 + 3 u − 4 u1/3), where u is the ratio of the nuclei volume to the volume of the cell. This result is universal, i.e., it does not depend on the applied nucleon interaction model within applied approach. For the innermost layers of inner crust u ∼ 0.2 leading to reduction of the shear modulus by $\sim 25\%$, which can be important for correct interpretation of quasi-periodic oscillations in the tails of magnetar flares.

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Neutron star crust in Voigt approximation II: general formula for electron screening correction for effective shear modulus

Cited by 3 publications

References 60 publications

Role of Quark Matter and Color Superconductivity in the Structure and Tidal Deformability of Strange Dwarfs

Role of Quark Matter and Color Superconductivity in the Structure and Tidal Deformability of Strange Dwarfs

Unmasking strange dwarfs with gravitational-wave observations

Neutron star inner crust: reduction of shear modulus by nuclei finite size effect

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