Particle motion around luminous neutron stars: effects of deviation from Schwarzschild spacetime

Fuente: arXiv
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Autores principales: Vieira, Ronaldo S. S., Wielgus, Maciek
Formato: Preprint
Publicado: 2024
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author Vieira, Ronaldo S. S.
Wielgus, Maciek
author_facet Vieira, Ronaldo S. S.
Wielgus, Maciek
contents We study trajectories of test particles around a luminous, static, spherically symmetric neutron star, under the combined influence of gravity and radiation. In general relativity, for Schwarzschild spacetime, an equilibrium sphere (the Eddington Capture Sphere) is formed for near-Eddington luminosities. We generalize these results to a broad class of static, spherical spacetimes. We also study the dynamics of particles in a strong radiation field in spherical spacetimes. The results are illustrated for two cases, Reissner-Nordström spacetime of a charged spherical object in general relativity and Kehagias-Sfetsos spacetime, arising from the Horava-Lifshitz gravity theory. Our findings apply to neutron stars under gravitational field equations different from the vacuum Einstein field equations of general relativity, such as in modified theories of gravity, the only requirement being that test particles follow geodesics in the absence of the radiation field. The effects that we describe are, in principle, measurable through observations of X-ray bursts of neutron stars. Hence, detailed future studies could use such observations to test gravity theories in the strong-field regime, provided that the impact of the spacetime geometry can be disentangled from the astrophysical uncertainties.
format Preprint
id arxiv_https___arxiv_org_abs_2403_01006
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Particle motion around luminous neutron stars: effects of deviation from Schwarzschild spacetime
Vieira, Ronaldo S. S.
Wielgus, Maciek
General Relativity and Quantum Cosmology
High Energy Astrophysical Phenomena
We study trajectories of test particles around a luminous, static, spherically symmetric neutron star, under the combined influence of gravity and radiation. In general relativity, for Schwarzschild spacetime, an equilibrium sphere (the Eddington Capture Sphere) is formed for near-Eddington luminosities. We generalize these results to a broad class of static, spherical spacetimes. We also study the dynamics of particles in a strong radiation field in spherical spacetimes. The results are illustrated for two cases, Reissner-Nordström spacetime of a charged spherical object in general relativity and Kehagias-Sfetsos spacetime, arising from the Horava-Lifshitz gravity theory. Our findings apply to neutron stars under gravitational field equations different from the vacuum Einstein field equations of general relativity, such as in modified theories of gravity, the only requirement being that test particles follow geodesics in the absence of the radiation field. The effects that we describe are, in principle, measurable through observations of X-ray bursts of neutron stars. Hence, detailed future studies could use such observations to test gravity theories in the strong-field regime, provided that the impact of the spacetime geometry can be disentangled from the astrophysical uncertainties.
title Particle motion around luminous neutron stars: effects of deviation from Schwarzschild spacetime
topic General Relativity and Quantum Cosmology
High Energy Astrophysical Phenomena
url https://arxiv.org/abs/2403.01006