Charged black holes in scalar-tensor gravity as gravitational lenses

ERNESTO F. EIROA; CARLOS M SENDRA (EXPOSITOR)

La Falda, Córdoba

Conferencia; Grav 15; 2015

FaMAF Universidad Nacional de Córdoba

The fact that black holes distort the spacetime structure in their surroundings, affecting therefore the paths of light rays, makes them interesting to study the situation in which they act as gravitational lenses. In particular, photons passing close enough to the photon sphere can perform one or more turns around the black hole before they emerge and reach an observer. This gives place to two infinite sets of relativistic images (one on each side of the lens) that can be studied by using the strong deflection limit, which corresponds to an asymptotic logarithmic approximation for the deflection angle. In the current standard model of the Universe, a negative pressure fluid called dark energy fills it, representing about 70 % of its total density, while the other 30 % corresponds to barionic and dark matter. Dark energy can be modeled by a self-interacting scalar field with a potential. In this work, we consider a class of static and spherically symmetric charged black holes in scalar-tensor gravity as gravitational lenses. We carry out the strong deflection limit to obtain analytical expressions for the deflection angle, and the positions and magnifications of the relativistic images. We compare the results obtained with those corresponding to the Reissner-Norstrom geometry, and we study the Galactic supermassive black hole as a numerical example.