Bristol Open-source Relativistic Gravity

How do supermassive black holes grow and affect their surroundings? Are the black holes spinning and behaving according to the predictions of General Relativity?

We intend to address these questions by carefully analysing the X-ray emission produced by hot gas as it spirals into a black hole.

Supermassive black holes are found at the centres of all galaxies. In a small fraction of these galaxies, gas falling into the vicinity of the black hole forms a thin, orbiting disc. As the matter in the disc slowly spirals inwards its gravitational potential energy is converted to kinetic energy, so the gas swirls around faster, and heat, which makes the matter glow brightly in X-rays. This dynamic environment produces X-rays that very in brightness on short timescales.

These flickering X-rays illuminate the swirling matter which imprints spectral features including emission lines. The emission can be blue-shifted or red-shifted and have its brightness modulated in a characteristic way due to the high velocity of the gas and the relativistic effects of the black hole. We have a new computer program that predicts what these X-rays should look like and how they should very in brightness for different scenarios - for example, different black hole spin rates, disc shapes, X-ray emission regions, and even for different models of gravity that are slightly different to general relativity.

By carefully comparing the details of our model predications with X-ray observations we can measure black hole masses, determine the disc and X-ray source geometries, and test general relativity near black holes.