Shadows and negative precession in non-Kerr spacetime

TL;DR

This paper explores how deformed Kerr spacetimes with naked singularities can exhibit both negative precession of bound orbits and distinctive shadows, providing potential observational signatures to distinguish such objects from black holes.

Contribution

It demonstrates that negative precession and shadow features can coexist in deformed Kerr naked singularity spacetimes, expanding understanding of observational signatures of exotic compact objects.

Findings

Negative precession occurs in deformed Kerr naked singularity spacetimes.

Shadow features of naked singularities are elaborated and distinguished from black holes.

Negative precession and shadow can coexist, aiding observational identification.

Abstract

It is now known that the shadow is not only the property of a black hole, it can also be cast by other compact objects like naked singularities. However, there exist some novel features of the shadow of the naked singularities which are elaborately discussed in some recent articles. In the earlier literature, it is also shown that a naked singularity may admit negative precession of bound timelike orbits which cannot be seen in Schwarzschild and Kerr black hole spacetimes. This distinguishable behavior of timelike bound orbit in the presence of the naked singularity along with the novel features of the shadow may be useful to distinguish between a black hole and a naked singularity observationally. However, in this paper, it is shown that deformed Kerr spacetime can allow negative precession of bound timelike orbits when the central singularity of that spacetime is naked. We also show that negative precession and shadow both can exist simultaneously in deformed Kerr naked singularity spacetime. Therefore, any observational evidence of negative precession of bound orbits, along with the central shadow may indicate the presence of a deformed Kerr naked singularity.