# Black Holes and Neutron Stars in Vector Galileons

## TL;DR

This paper explores black holes and neutron stars within a vector Galileon gravity theory, revealing new solutions and properties that could distinguish these objects observationally from their General Relativity counterparts.

## Contribution

It introduces and analyzes spherically symmetric black hole and neutron star solutions in a one-parameter vector Galileon theory, highlighting their unique features and potential observational signatures.

## Key findings

- Black holes in the theory are more compact than in GR.
- Neutron stars can be more massive and compact, possibly exceeding Schwarzschild black holes.
- The solutions extend known results from GR and scalar-tensor theories.

## Abstract

The direct detection of gravitational waves opens new perspectives for measuring properties of gravitationally bound compact objects. It is then important to investigate black holes and neutron stars in alternative theories of gravity, since they can have features that make them observationally distinguishable from their General Relativity (GR) counterparts. In this work, we examine a special case of vector Galileons, a vector-tensor theory of gravity with interesting cosmological properties, which consists of a one parameter modification of the Einstein-Maxwell action. Within this theory, we study configurations describing asymptotically flat, spherically symmetric black holes and neutron stars. The set of black hole solutions in this theory is surprisingly rich, generalising results found in GR or in related scalar-tensor theories. We investigate the properties and conserved charges of black holes, using both analytical and numerical techniques, highlighting configurations that are more compact than in GR. We then study properties of neutron stars, showing how the vector profile can influence the star internal structure. Depending on properties of matter and fields inside the star, neutron stars can be more massive than in GR, and they can be even more compact than Schwarzschild black holes, making these objects observationally interesting. We also comment on possible extensions of our configurations to magnetically charged or rotating configurations.