Regular phantom black holes as gravitational lenses

ERNESTO F. EIROA; CARLOS M SENDRA (EXPOSITOR)

Buenos Aires

Conferencia; Gravitation, Astrophysics and Cosmology - II Argentinian-Brazilian Meeting; 2014

The distortion of the spacetime structure in the surroundings of black holes affects the trajectories of light rays. As a consequence, black holes can act as gravitational lenses. Observations of type Ia supernovas, show that our Universe is in accelerated expansion. The usual explanation is that the Universe is filled with a negative pressure fluid called dark energy, which accounts for 70% of its total density, which can be modeled by a self-interacting scalar field with a potential. We consider a class of spherically symmetric regular phantom black holes as gravitational lenses. First, for small deflection angles, we perform the weak deflection limit to obtain the positions and the magnifications of the primary and secondary images of a point source. For large deflection angles we use the strong deflection limit, corresponding to an asymptotic logarithmic approximation. In this case, photons pass close to the photon sphere of the black hole and experiment several loops around it before they emerge to the observer, giving place to two in finite sets of relativistic images. Within this limit, we find analytical expressions for the positions and the magnifications of these images, and the time delays between them. Finally, we discuss the results obtained and make a comparison with the Schwarzschild and Brans-Dicke solutions for the case of the galactic center supermassive black hole.