Iron Line Spectroscopy of Black Holes in Vector-Tensor Galileons Modified Gravity

TL;DR

This paper investigates whether iron line spectroscopy can distinguish black holes in Vector-Tensor Galileons modified gravity from Kerr black holes, suggesting current X-ray observations could test this alternative gravity theory.

Contribution

It introduces a new black hole solution in Vector-Tensor Galileons gravity and assesses its observational signatures via iron line spectroscopy.

Findings

Current X-ray facilities can potentially test the new black hole solution.

Iron line shapes differ between the Vector-Tensor Galileons black hole and Kerr.

Constraints on the modified gravity theory are possible in certain regimes.

Abstract

Recently, a rotating black hole solution was found in Vector-Tensor Galileons modified gravity that has some significant differences from the Kerr black hole solution. We study the iron line shape that is part of the reflection spectrum of accretion disks around black holes in this new black hole solution. We simulate and compare the iron lines of this solution with those of the Kerr solution to see if the technique of iron line spectroscopy can be used as a tool to test Vector-Tensor Galileons modified gravity. Our analysis shows that current X-ray facilities can, in principle, be used to test and place constraints on Vector-Tensor Galileons modified gravity in the strong coupling and ultraspinning regimes.