Rapidly rotating neutron stars with a massive scalar field—structure and universal relations

Doneva, Daniela D.; Yazadjiev, Stoytcho S.

doi:10.1088/1475-7516/2016/11/019

Cited by 79 publications

(64 citation statements)

References 77 publications

(117 reference statements)

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“…Pretorius [334] found that neutron stars (and not white dwarves) can scalarize and evade these observational bounds at the same time when −10 −3 ≲ β ≲ −3 and 10 −16 eV ≪ m s ≲ 10 −9 eV. Doneva and Yazadjiev [332] found that the universality in the I-Q relation is worse than that in GR, though the former remains equation-of-state universal within a few percent for a fixed f s M (where we recall f s is the stellar spin frequency). They also found that such a relation deviates from that in GR by 20% at most for β = −6 and Φ ∞ E,0 = 0.…”

Section: Scalar-tensor Theoriesmentioning

confidence: 95%

“…with m s is the mass of the scalar field. Spontaneous scalarization in such a theory was first studied in [333,334] for non-rotating neutron stars, and was later extended to slowly-rotating [335] and rapidly-rotating [332] neutron stars. The advantage of considering a massive theory is that if the scalar field mass is sufficiently large, non-GR modifications are screened and one is likely to evade Solar System and binary pulsar bounds on β for the massless theory.…”

Section: Scalar-tensor Theoriesmentioning

confidence: 99%

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Approximate universal relations for neutron stars and quark stars

2017

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Neutron stars and quark stars are ideal laboratories to study fundamental physics at supra nuclear densities and strong gravitational fields. Astrophysical observables, however, depend strongly on the star's internal structure, which is currently unknown due to uncertainties in the equation of state. Universal relations, however, exist among certain stellar observables that do not depend sensitively on the star's internal structure. One such set of relations is between the star's moment of inertia (I), its tidal Love number (Love) and its quadrupole moment (Q), the so-called I-Love-Q relations. Similar relations hold among the star's multipole moments, which resemble the well-known black hole no-hair theorems. Universal relations break degeneracies among astrophysical observables, leading to a variety of applications: (i) X-ray measurements of the nuclear matter equation of state, (ii) gravitational wave measurements of the intrinsic spin of inspiraling compact objects, and (iii) gravitational and astrophysical tests of General Relativity that are independent of the equation of state. We here review how the universal relations come about and all the applications that have been devised to date. Contents 3.2.

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Section: Scalar-tensor Theoriesmentioning

confidence: 95%

Section: Scalar-tensor Theoriesmentioning

confidence: 99%

Approximate universal relations for neutron stars and quark stars

2017

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“…The structure and properties of slowly rotating neutron stars have also been explored under the influence of a massive scalar field. Doneva and Yazadjiev [27] investigated the dynamics of rapidly rotating neutron stars in the presence of a massive scalar field and concluded that deviations from GR can be large due to larger moment of inertia. Staykov et al [28] extended this work by considering a self-interacting potential along with a massive scalar field to analyze the behavior of static and slowly rotating neutron stars.…”

Section: Introductionmentioning

confidence: 99%

Anisotropic strange stars through embedding technique in massive Brans–Dicke gravity

Sharif

Majid

2020

Eur. Phys. J. Plus

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This paper investigates the existence and properties of anisotropic strange quark stars in the context of massive Brans-Dicke theory. The field equations are constructed in Jordan frame by assuming a suitable potential function with MIT bag model. We employ the embedding class-one approach as well as junction conditions to determine the unknown metric functions. Radius of the strange star candidate, LMC X-4, is predicted through its observed mass for different values of the bag constant. We analyze the effects of coupling parameter as well as mass of scalar field on state determinants and execute multiple checks on the stability and viability of the spherical system. It is concluded that the resulting stellar structure is physically viable and stable as it satisfies the energy conditions as well as essential stability criteria.

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“…The maximum mass that a differentially rotating neutron star can sustain therefore is higher for scalarized model than for GR models (with a strong dependence on the particular value of β). Notice that in the present paper we compare differentially rotating sequences of scaralized models with constant J to their GR counterparts, whereas in [24,25] sequences at the mass-shedding limit were considered (this explains the somewhat smaller deviations from GR, for same β, in the current results, with respect to those observerd in [24,25]).…”

Section: A Constant Angular Momentum Sequencesmentioning

confidence: 70%

Differentially rotating neutron stars in scalar-tensor theories of gravity

et al. 2018

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We present the first numerical models of differentially rotating stars in alternative theories of gravity. We chose a particular class of scalar-tensor theories of gravity that is indistinguishable from GR in the weak field regime but can lead to significant deviations when strong fields are considered. We show that the maximum mass that a differentially rotating neutron star can sustain increases significantly for scalarized solutions and such stars can reach larger angular momenta. In addition, the presence of a nontrivial scalar field has the effect of increasing the required axis ratio for reaching a given value of angular momentum, when compared to a corresponding model of same rest mass in general relativity. We find that the scalar field also makes rapidly rotating models less quasi-toroidal than their general-relativistic counterparts. For large values of the angular momentum and values of the coupling parameter that are in agreement with the observations, we find a second turning point for scalarized models along constant angular momentum sequences, which could have interesting implications for the stability of remnants created in a binary neutron star merger. * Electronic address: daniela.doneva@uni-tuebingen.de † Electronic address: yazad@phys.uni-sofia.bg ‡ Electronic address: niksterg@auth.gr § Electronic address: kostas.kokkotas@uni-tuebingen.de

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Rapidly rotating neutron stars with a massive scalar field—structure and universal relations

Cited by 79 publications

References 77 publications

Approximate universal relations for neutron stars and quark stars

Approximate universal relations for neutron stars and quark stars

Anisotropic strange stars through embedding technique in massive Brans–Dicke gravity

Differentially rotating neutron stars in scalar-tensor theories of gravity

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