Gravitationally captured, luminous material flowing onto neutron stars and black holes allows us to probe strong gravity in the relativistic regime, and the fundamental nature of space-time, albeit encoded via complex magnetohydrodynamic (MHD) flow dynamics and radiation physics. API research is founding and world-leading in using X-ray timing of Galactic X-ray binaries for this purpose. This research has now broadened to the emerging field of spectral timing, and to include supermassive black holes in active galactic nuclei (AGN), using novel techniques and data that allow better views of the various components of the inner flow.
The study of matter flowing into deep potential wells, its radiation, and the possible formation of jets from those accretion flows has long been a core topic of study at API. Over the past 4 years, significant advances have been made in both observations and theoretical simulations of relativistic accretion flows and jets. Two sensational observational firsts were achieved: imaging an accretion disc of a supermassive black hole and detecting the jets that emerge from an accreting neutron star. In both of these projects, API scientists played a leading role in both the theoretical and computational efforts, and the observational campaigns themselves. Additionally, novel computational methods were developed that increased the capability of simulating the magnetohydrodynamical flows around compact objects.
Now: RXTE archive, Swift, NICER, Chandra, AstroSAT, XMM-Newton, EHT, large-scale computing
Future: eXTP, ATHENA