One step closer to understand quasi-periodic oscillations in black hole accretion disks

Group member Dr. Gibwa Musoke lead a study wherein we discovered a possible origin for quasi-periodic oscillations in black hole accretion disks. Once a thin accretion disk is strongly tilted with respect to the black hole spin axis, it can tear off into differentially precessing sub-disks. In the high-resolution GRMHD simulation analyzed by Gibwa, we found that not only does the tearing yield an explanation to the so-called low-frequency quasi periodic oscillations which are a consequence from the precession of the inner sub-disk, the inner disk also performs rapid "breathing oscillations" which can explain the Quasi-periodic signals observed from some X-ray binary disks at very high luminosity.

The paper has now been accepted for publication in MNRAS. See the full press release or just head over to the simulation movie made by co-Author Dr. Matthew Liska.

3rd Dec 2022 by Oliver
tags: science

The gentle giant

The picture of our very own black hole is finally out. Glad to have played a small role in its interpretation in the BlackHoleCam and EventHorizonTelescope collaborations. See here for all the 10(!!) papers. But if you are in a hurry check out paper V which shows the large role of computational physics in today's discovery.

12th May 2022 by Oliver
tags: science

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Relativistic plasma dynamics


With numerical simulations of accreting compact objects, we study the transport of angular momentum and magnetic field, the ejection of relativistic jets and model horizon scale structure observed by the Event Horizon Telescope.

Pulsar Wind Nebulae

PWN are unique laboratories to investigate relativistic plasma. Among other things, they teach us about fluid instabilities, relativistic shocks, magnetic dissipation, particle acceleration and turbulent processes.

Radiative signatures

By modeling the non-thermal radiation emitted from astrophysical plasma, we extract important source parameters and understand particle energetization in a regime impossible to study in the laboratory.

Computational methods

The main tools of my research

Black Hole Accretion Code [BHAC]

Build upon the MPI-AMRVAC framework, the Black Hole Accretion Code solves the equations of general relativistic magnetohydrodynamics (GRMHD). Its modular design allows to simulate not only Einstein gravity, but also Black Holes in arbitrary metric theories of gravity and other compact objects. BHAC is the workhorse GRMHD-code for the blackholecam collaboration and provides source models for the Event Horizon Telescope Collaboration.

Adaptive Mesh Refinement Versatile Advection Code [MPI-AMRVAC]

With a current focus on solar- and non-relativistic astrophysical applications, MPI-AMRVAC offers a wide range of advanced features for the solution of (quasi-) conservation laws. Adaptive grids can be employed in cartesian, cylindrical and (stretched) spherical geometries. The code has been modernized recently and the documentation is frequently updated.