Gravitational Lensing Effects of Fermion-Fermion Stars: I. Strong Field Case

TL;DR

This paper models fermion-fermion stars as gravitational lenses, revealing complex image formations and critical curves, which could help distinguish dark matter structures through astronomical observations.

Contribution

It introduces a two-component fermion-fermion star model for gravitational lensing, showing unique image configurations not seen in single-component models.

Findings

Multiple images and critical curves identified in the model.

Presence of Einstein rings and radial critical curves.

Potential observational signatures for dark matter structures.

Abstract

We investigate a two-component model for gravitational lenses, i.e., the fermion-fermion star as a dark matter self-gravitating system made from two kinds of fermions with different masses. We calculate the deflection angles varying from arcseconds to even degrees. There is one Einstein ring. In particular, we find three radial critical curves for radial magnifications and four or five images of a point source. These are different from the case of the one-component model such as the fermion stars and boson stars. This is due to the fermion-fermion star being a two-component concentric sphere. Our results suggest that any possible observations of the number of images more than 3 could imply a polytropic distribution of the mass inside the lens in the universe.