An accurate metric for the spacetime around neutron stars

Abstract

The problem of having an accurate description of the spacetime around neutron stars is of great astrophysical interest. For astrophysical applications, one needs to have a metric that captures all the properties of the spacetime around a neutron star. Furthermore, an accurate appropriately parameterised metric, i.e., a metric that is given in terms of parameters that are directly related to the physical structure of the neutron star, could be used to solve the inverse problem, which is to infer the properties of the structure of a neutron star from astrophysical observations. In this work we present such an approximate stationary and axisymmetric metric for the exterior of neutron stars, which is constructed using the Ernst formalism and is parameterised by the relativistic multipole moments of the central object. This metric is given in terms of an expansion on the Weyl-Papapetrou coordinates with the multipole moments as free parameters and is shown to be extremely accurate in capturing the physical properties of a neutron star spacetime as they are calculated numerically in general relativity. Because the metric is given in terms of an expansion, the expressions are much simpler and easier to implement, in contrast to previous approaches. For the parameterisation of the metric in general relativity, the recently discovered universal 3-hair relations are used to produce a 3-parameter metric. Finally, a straightforward extension of this metric is given for scalar-tensor theories with a massless scalar field, which also admit a formulation in terms of an Ernst potential.

References in corpus (15)

• Testing the black hole "no-hair" hypothesis
• Formation of millisecond pulsars with CO white dwarf companions - II. Accretion, spin-up, true ages and comparison to MSPs with He white dwarf companions
• A quasi-periodic modulation of the iron line centroid energy in the black hole binary H 1743-322
• The Oblate Schwarzschild Approximation for Light Curves of Rapidly Rotating Neutron Stars
• Testing the space-time geometry around black hole candidates with the analysis of the broad K$\alpha$ iron line
• Rotating proto-neutron stars: spin evolution, maximum mass and I-Love-Q relations
• Universal I-Q relations for rapidly rotating neutron and strange stars in scalar-tensor theories
• Orbital and epicyclic frequencies around rapidly rotating compact stars in scalar-tensor theories of gravity
• Multipole moments in scalar-tensor theory of gravity
• Realistic Exact Solution for the Exterior Field of a Rotating Neutron Star
• An all-purpose metric for the exterior of any kind of rotating neutron star
• Epicyclic frequencies for rotating strange quark stars: the importance of stellar oblateness
• Faithful transformation of quasi-isotropic to Weyl-Papapetrou coordinates: A prerequisite to compare metrics
• Multipole Moments of numerical spacetimes
• High Frequency QPOs in Neutron Stars and Black Holes: Probing Dense Matter and Strong Gravitational Fields

Cited by in corpus (5)

• Extreme-mass-ratio inspirals into rotating boson stars: nonintegrability, chaos, and transient resonances
• Epicyclic oscillations in the Hartle-Thorne external geometry
• Universal Relations for rapidly rotating neutron stars using supervised machine-learning techniques
• An Approximate Kerr-Newman-like Metric Endowed with a Magnetic Dipole and Mass Quadrupole
• Dynamics of magnetoviscous warped discs around compact objects