Accretion : Inflow & Outflows

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.

Historically

API research has been very strong in exploiting new developments in HEA instrumentation, for instance being world leading in using X-ray timing of Galactic X-ray binaries.

The study of matter flowing into deep potential wells, its radiation, and the possible formation of outflows from those accretion flows has long been a core topic of study at API.

Over the past few years, we have made significant advances in both :
- observations and theoretical simulations of relativistic accretion flows and jets, - and more recently also the study of disk winds.

We had leading roles in two recent sensational observational firsts:
- the imaging of the light from just outside the event horizon of the supermassive black hole in the M87 galaxy
- and the detection of jets emerging from a strongly magnetised accreting neutron star.

For both projects, we were involved in both the observations as well as the theoretical modelling and interpretation.

Current studies

We are actively developing novel computational methods to increase the capability of simulating the magneto-hydrodynamical flows around compact objects.

This research has broadened to the emerging field of multi-wavelength observations and spectral-timing, and extends to supermassive black holes in active galactic nuclei (AGN).

We apply novel multi-wavelength observational methods combined with state-of-the-art computational models that allow us to dissect the various components of the accretion flow around the compact object, as well as the jets and disk winds that are produced.

We also study how the physics of accretion and associated outflows scales with black hole mass and between compact objects of various types.

Keywords

Accretion disks, black holes, neutron stars, active galactic nuclei (AGN), X-ray binaries, jets, disk winds, numerical simulations, multi-wavelength observations, radiatively inefficient accretion flows, magnetic accretion, time-series analysis

Facilities
Now: Fermi, Rossi X-ray Timing Explorer (RXTE) archive, Neil Gehrels Swift Observatory (Swift), Neutron Star Interior Composition Explorer (NICER), Chandra X-ray Observatory, AstroSAT, XMM-Newton, Suzaku, NuSTAR, Hubble Space Telescope (HST), Very Large Telescope (VLT), MeerLICHT, MeerKAT, Jansky Very Large Array (VLA), Atacama Telescope Compact Array (ATCA), Event Horizon Telescope (EHT), large-scale computing

Future: Cherenkov Telescope Array (CTA), enhanced X-ray Timing and Polarimetry mission (eXTP), ATHENA, X-ray Imaging and Spectroscopy Mission (XRISM), SKA