Time delay and magnification centroid due to gravitational lensing by black holes and naked singularities

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dc.creatorVirbhadra, K. S.
dc.creatorKeeton, C. R.
dc.date2007-10-11
dc.date.accessioned2026-07-07T11:38:02Z
dc.date.available2026-07-07T11:38:02Z
dc.descriptionWe model the massive dark object at the center of the Galaxy as a Schwarzschild black hole as well as Janis-Newman-Winicour naked singularities, characterized by the mass and scalar charge parameters, and study gravitational lensing (particularly time delay, magnification centroid, and total magnification) by them. We find that the lensing features are qualitatively similar (though quantitatively different) for the Schwarzschild black holes, weakly naked, and marginally strongly naked singularities. However, the lensing characteristics of strongly naked singularities are qualitatively very different from those due the Schwarzschild black holes. The images produced by Schwarzschild black hole lenses and weakly naked and marginally strongly naked singularity lenses always have positive time delays. On the other hand, the strongly naked singularity lenses can give rise to images with positive, zero, or negative time delays. In particular, for a large angular source position the direct image (the outermost image on the same side as the source) due to strongly naked singularity lensing always has negative time delay. We also found that the scalar field decreases the time delay and increases the magnitude of magnifications of images; this result could have important implications for cosmology. As the Janis-Newman-Winicour metric also describes the exterior gravitational field of a scalar star, naked singularities as well as scalar star lenses, if these exist in nature, will serve as more efficient cosmic telescopes than regular gravitational lenses.
dc.descriptionRevTex, 14 pages, 5 figures
dc.identifierhttps://arxiv.org/abs/0710.2333
dc.identifierhttp://arxiv.org/abs/0710.2333
dc.identifierPhys.Rev.D77:124014,2008
dc.identifierdoi:10.1103/PhysRevD.77.124014
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/199418
dc.subjectGeneral Relativity and Quantum Cosmology
dc.subjectAstrophysics
dc.subjectHigh Energy Physics - Theory
dc.subjectClassical Physics
dc.titleTime delay and magnification centroid due to gravitational lensing by black holes and naked singularities
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