Testing Horndeski gravity with S2 star orbit

TL;DR

This paper introduces a novel method to constrain Horndeski gravity by analyzing the orbit of the S2 star, using a generalized Yukawa potential at the Newtonian level, providing new bounds on the theory's parameters.

Contribution

It demonstrates the feasibility of using weak-field orbital data to test and constrain Horndeski gravity, a previously underexplored regime for this theory.

Findings

Two parameters constrained with unprecedented precision.

Remaining parameters have exclusion regions.

Potential for future weak-field tests to further constrain the theory.

Abstract

We have explored a completely new and alternative way to restrict the parameter space of Horndeski theory of gravity. Using its Newtonian limit, it is possible to test the theory at a regime where, given its complexity and the small magnitude of the expected effects, it is poorly probed. At Newtonian level, it gives rise to a generalized Yukawa-like Newtonian potential which we have tested using S2 star orbit data. Our model adds five parameters to the General Relativity model, and the analysis constrains two of them with unprecedented precision to these energy scales, while only gives an exclusion region for the remaining parameters. We have shown the potential of weak-field tests to constrain Horndeski gravity opening, as a matter of fact, a new avenue that deserves to be further, and deeply, explored near in the future.