Tidal deformations of neutron stars with elastic crusts

Gittins, Fabian; Andersson, Nils; Pereira, Jonas P.

doi:10.1103/physrevd.101.103025

Cited by 44 publications

(59 citation statements)

References 49 publications

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“…Focusing on the role of the matter model in our calculations, we found that the point where the strain was the largest for all the forces we considered was the top of the crust. This is where the crust yields which is consistent with previous calculations of neutron star crusts (Gittins et al 2020(Gittins et al , 2021. In Fig.…”

Section: A Solution To the Relativistic Laplace's Equationsupporting

confidence: 92%

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Modelling neutron star mountains

Gittins

Andersson

Jones

2020

Monthly Notices of the Royal Astronomical Society

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As the era of gravitational-wave astronomy has well and truly begun, gravitational radiation from rotating neutron stars remains elusive. Rapidly spinning neutron stars are the main targets for continuous-wave searches since, according to general relativity, provided they are asymmetrically deformed, they will emit gravitational waves. It is believed that detecting such radiation will unlock the answer to why no pulsars have been observed to spin close to the break-up frequency. We review existing studies on the maximum mountain that a neutron star crust can support, critique the key assumptions and identify issues relating to boundary conditions that need to be resolved. In light of this discussion, we present a new scheme for modelling neutron star mountains. The crucial ingredient for this scheme is a description of the fiducial force which takes the star away from sphericity. We consider three examples: a source potential which is a solution to Laplace’s equation, another solution which does not act in the core of the star and a thermal pressure perturbation. For all the cases, we find that the largest quadrupoles are between a factor of a few to two orders of magnitude below previous estimates of the maximum mountain size.

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Section: A Solution To the Relativistic Laplace's Equationsupporting

confidence: 92%

“…Since 0 needed to have a finite value at the base of the crust in the fluid star, we effectively violated the radial traction condition [cf. (A17) in Gittins et al (2020)]. However, we can still use the tangential traction condition to demand 2 ( base ) = 0.…”

Section: A Thermal Pressure Perturbation Outside the Corementioning

confidence: 99%

Modelling neutron star mountains

Gittins

Andersson

Jones

2020

Monthly Notices of the Royal Astronomical Society

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“…At the same time, more and louder detections offer the opportunity of going beyond a single radius measurement [140] or even a characterization of features of the equation of state such as phase transitions [123]. Improved detector sensitivity will allow us to measure higher order terms beyond the = 2 tidal deformability [74], directly observe the postmerger signal [38], and study the properties of the neutron star crust in terms of its elastic properties [334,335], heating [336], and shattering [337]. Another effect of interest is the potential resonant excitation of different neutron star modes driven by the orbital motion [338,339].…”

Section: Future Challenges and Opportunitiesmentioning

confidence: 99%

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

2020

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Despite their long history and astrophysical importance, some of the key properties of neutron stars are still uncertain. The extreme conditions encountered in their interiors, involving matter of uncertain composition at extreme density and isospin asymmetry, uniquely determine the stars' macroscopic properties within General Relativity. Astrophysical constraints on those macroscopic properties, such as neutron star masses and radii, have long been used to understand the microscopic properties of the matter that forms them. In this article we discuss another astrophysically observable macroscopic property of neutron stars that can be used to study their interiors: their tidal deformation. Neutron stars, much like any other extended object with structure, are tidally deformed when under the influence of an external tidal field. In the context of coalescences of neutron stars observed through their gravitational wave emission, this deformation, quantified through a parameter termed the tidal deformability, can be measured. We discuss the role of the tidal deformability in observations of coalescing neutron stars with gravitational waves and how it can be used to probe the internal structure of Nature's most compact matter objects. Perhaps inevitably, a large portion of the discussion will be dictated by GW170817, the most informative confirmed detection of a binary neutron star coalescence with gravitational waves as of the time of writing.

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“…We assume that the onset of the crust elasticity is at 2 × 10 14 g cm −3 and that it finishes at 10 7 g cm −3 , where the liquid ocean/envelope is supposed to start (Pereira et al 2020). It is already known that such a shear modulus leads to negligible tidal deformation changes in ordinary NSs (Penner et al 2011;Gittins et al 2020), described in terms of zerofrequency non-radial perturbations. Therefore, one would expect that for other types of perturbations, they would also lead to negligible changes when compared to the perfect-fluid results.…”

Section: Shear Modulus For the Hadronic Phasementioning

confidence: 99%

Probing Elastic Quark Phases in Hybrid Stars with Radius Measurements

Pereira

Bejger

Tonetto

et al. 2021

ApJ

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The internal composition of neutron stars is currently largely unknown. Due to the possibility of phase transitions in quantum chromodynamics, stars could be hybrid and have quark cores. We investigate some imprints of elastic quark phases (only when perturbed) on the dynamical stability of hybrid stars. We show that they increase the dynamical stability window of hybrid stars in the sense that the onset of instabilities happens at larger central densities than the ones for maximum masses. In particular, when the shear modulus of a crystalline quark phase is taken at face value, the relative radius differences between elastic and perfect-fluid hybrid stars with null radial frequencies (onset of instability) would be up to 1%-2%. Roughly, this would imply a maximum relative radius dispersion (on top of the perfect-fluid predictions) of 2%-4% for stars in a given mass range exclusively due to the elasticity of the quark phase. In the more agnostic approach where the estimates for the quark shear modulus only suggest its possible order of magnitude (due to the many approximations taken in its calculation), the relative radius dispersion uniquely due to a quark phase elasticity might be as large as 5%-10%. Finally, we discuss possible implications of the above dispersion of radii for the constraint of the elasticity of a quark phase with electromagnetic missions such as NICER, eXTP, and ATHENA.Unified Astronomy Thesaurus concepts: General relativity (641); Neutron stars (1108); Stellar oscillations (1617)

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Tidal deformations of neutron stars with elastic crusts

Cited by 44 publications

References 49 publications

Modelling neutron star mountains

Modelling neutron star mountains

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

Probing Elastic Quark Phases in Hybrid Stars with Radius Measurements

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