Accreting black holes at all scales – From X-ray binaries to galactic centers – Ileyk El Mellah

Black holes are key players in astrophysical phenomena across scales, from shaping galaxy evolution to powering X-ray binaries. The emission from the plasma they accrete provides a unique opportunities to probe physics under extreme gravitational, magnetic, and radiative conditions. The discovery of merging stellar-mass black holes in 2015 established stellar binaries as likely progenitors, though the complexities of mass transfer remain a significant challenge. On larger scales, observations from the Event Horizon Telescope (EHT) have revealed the highly magnetized, relativistic environments around accreting supermassive black holes, shedding light on jet formation and particle acceleration.

Advances in 3D multi-scale, multi-physics simulations have bridged the gap between scales. In X-ray binaries, we can now closely monitor critical mass transfer processes, from the stellar photosphere all the way down to the black hole’s event horizon. Global 3D particle-in-cell simulations in curved spacetime of black holes’ coronae have revealed electron acceleration via magnetic reconnection in the jet sheath. These cutting-edge simulations, powered by adaptive mesh refinement and GPU-parallelization, have provided unprecedented insights into turbulent plasma, magnetic field dynamics and jet formation, with application to supermassive black holes like Sagittarius A*. These findings not only deepen our understanding of accreting black holes but also emphasize the need for sustained observational and computational investments, such as ALMA and supercomputing facilities like Geryon.