Testing general relativity with accretion onto compact objects

TL;DR

This paper discusses how high-resolution X-ray observations of accreting neutron stars and black holes can test fundamental physics questions like the validity of general relativity and the Kerr metric in strong gravity regimes.

Contribution

It proposes using upcoming advancements in TES technology for high-spectral and high-timing resolution to investigate spacetime around compact objects.

Findings

Potential to test general relativity in strong gravity

Reverberation mapping and QPOs as diagnostic tools

Future X-ray technology enables new tests of spacetime geometry

Abstract

The X-ray emission of neutron stars and black holes presents a rich phenomenology that can lead us to a better understanding of their nature and to address more general physics questions: Does general relativity apply in the strong gravity regime? Is spacetime around black holes described by the Kerr metric? This white paper considers how we can investigate these questions by studying reverberation mapping and quasi-periodic oscillations in accreting systems with a combination of high-spectral and high-timing resolution. In the near future, we will be able to study compact objects in the X-rays in a new way: advancements in transition-edge sensors (TES) technology will allow for electron-volt-resolution spectroscopy combined with nanoseconds-precision timing.