Revising the Multipole Moments of Numerical Spacetimes and its Consequences

We construct sequences of rapidly rotating neutron stars in dilatonic Einstein-Gauss-Bonnet theory, employing two equations of state for the nuclear matter. We analyze the dependence of the physical properties of these neutron stars on the Gauss-Bonnet coupling strength. For a given equation of state we determine the physically relevant domain of rapidly rotating neutron stars, which is delimited by the set of neutron stars rotating at the Kepler limit, the set of neutron stars along the secular instability line, and the set of static neutron stars. As compared to Einstein gravity, the presence of the Gauss-Bonnet term decreases this domain, leading to lower values for the maximum mass as well as to smaller central densities. The quadrupole moment is decreased by the GaussBonnet term for rapidly rotating neutron stars, while it is increased for slowly rotating neutron stars. The universal relation between the quadrupole moment and the moment of inertia found in General Relativity appears to extend to dilatonic Einstein-Gauss-Bonnet theory with very little dependence on the coupling strength of the Gauss-Bonnet term. The neutron stars carry a small dilaton charge.

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“…We employ the definitions of Geroch and Hansen [79,80], and follow closely the later references [81][82][83].…”

Section: Discussionmentioning

confidence: 99%

“…Note, that in the vacuum limit, when the dilaton charge vanishes, the quadrupole moment Q is the same as in [83] (up to an overall sign),…”

Section: Appendix A: Quadrupole Momentmentioning

confidence: 99%

Rapidly rotating neutron stars in dilatonic Einstein-Gauss-Bonnet theory

et al. 2016

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“…Further evidence to support the quadratic relation Eq. (8) is given in [69,70]. The authors of [69,71] also point out a spin correction in the identification of multipole moments that was previously overlooked; this correction preserves the quadratic spin behaviour of Eq.…”

Section: Quadrupole-monopole Effectsmentioning

confidence: 99%

Constraining the neutron star equation of state with gravitational wave signals from coalescing binary neutron stars

et al. 2015

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Recently exploratory studies were performed on the possibility of constraining the neutron star equation of state (EOS) using signals from coalescing binary neutron stars, or neutron star-black hole systems, as they will be seen in upcoming advanced gravitational wave detectors such as Advanced LIGO and Advanced Virgo. In particular, it was estimated to what extent the combined information from multiple detections would enable one to distinguish between different equations of state through hypothesis ranking or parameter estimation. Under the assumption of zero neutron star spins both in signals and in template waveforms and considering tidal effects to 1PN order, it was found that O(20) sources would suffice to distinguish between a stiff, moderate, and soft equation of state. Here we revisit these results, this time including neutron star tidal effects to the highest order currently known, termination of gravitational waveforms at the contact frequency, neutron star spins, and the resulting quadrupole-monopole interaction. We also take the masses of neutron stars in simulated sources to be distributed according to a relatively strongly peaked Gaussian, as hinted at by observations, but without assuming that the data analyst will necessarily have accurate knowledge of this distribution for use as a mass prior. We find that especially the effect of the latter is dramatic, necessitating many more detections to distinguish between different EOS and causing systematic biases in parameter estimation, on top of biases due to imperfect understanding of the signal model pointed out in earlier work. This would get mitigated if reliable prior information about the mass distribution could be folded into the analyses.PACS numbers: 26.60. Kp, 95.85.Sz

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“…Thus the expressions for the quadrupole moment are completely analogous. In the vacuum limit, when the dilaton charge vanishes, the quadrupole moment Q reduces to the expression in [29] (up to an overall sign),…”

Section: Einstein-gauss-bonnet-dilaton Theorymentioning

confidence: 99%

Quadrupole moments of rapidly rotating compact objects in dilatonic Einstein-Gauss-Bonnet theory

2014

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We consider rapidly rotating black holes and neutron stars in dilatonic Einstein-Gauss-Bonnet (EGBd) theory and determine their quadrupole moments, which receive a contribution from the dilaton. The quadrupole moment of EGBd black holes can be considerably larger than the Kerr value. For neutron stars, the universality property of theÎ-Q relation between the scaled moment of inertia and the scaled quadrupole moment appears to extend to EGBd theory.

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Revising the Multipole Moments of Numerical Spacetimes and its Consequences

Cited by 123 publications

References 33 publications

Rapidly rotating neutron stars in dilatonic Einstein-Gauss-Bonnet theory

Rapidly rotating neutron stars in dilatonic Einstein-Gauss-Bonnet theory

Constraining the neutron star equation of state with gravitational wave signals from coalescing binary neutron stars

Quadrupole moments of rapidly rotating compact objects in dilatonic Einstein-Gauss-Bonnet theory

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