Seminar

Povzetek

Quasi-periodic eruptions (QPEs) are newly discovered transients of unknown nature occurring near supermassive black holes, which feature bright X-ray bursts separated by approximately 10 hours. A promising model for QPEs is the star-disc model, where a star interacts periodically with a black hole’s pre-existing accretion disc, creating shocks that expel dense gas clouds from which radiation emerges.
We performed the first 3D radiation-hydrodynamics simulations to investigate the dynamics of the star-disc collisions, the properties of the ejected gas clouds, and the resulting radiation signatures. The star was modeled as a solid, spherical body, and the interaction was simulated for a small, local section of the accretion disc.
We found that star-disc collisions generate a nearly paraboloidal bow shock. The heating of gas is not confined to the column of gas directly ahead of the star but also extends laterally as the shock front expands sideways while traveling with the star. The collision drives an outflow of gas both in the forward and backward directions relative to the star’s motion. These outflows are asymmetric, with the forward outflow carrying more mass and producing a brighter luminosity than the backward component. We found that variations in stellar size, velocity, and disc density systematically influence this asymmetry, suggesting that specific parameter combinations could naturally reproduce the strong-weak brightness pattern observed in some QPEs.