ASTRODEBATA / Taj Jankovič: Mysterious X-ray Flares Near Black Holes: Are They Caused by Star-Disc Collisions?

Mysterious X-ray Flares Near Black Holes: Are They Caused by Star-Disc Collisions?

Taj Jankovič
FZU - Institute of Physics, Czech Academy of Sciences

Astronomers have recently discovered a puzzling type of cosmic flare – brief but powerful X-ray bursts that repeat every few hours near supermassive black holes. These events, known as quasi-periodic eruptions (QPEs), remain an unsolved mystery. What causes these flares? And why do they often alternate between longer and shorter intervals or stronger and weaker bursts? One of the most promising explanations is a star repeatedly colliding with a black hole’s accretion disc – a ring of gas orbiting around the black hole. To test this idea, we performed radiation-hydrodynamics simulations of star-disc collisions and studied how they unfold. Our results show that the impact creates shock waves that expel dense gas clouds in both forward and backward directions. However, these outflows can be asymmetric – the forward-moving gas carries more mass and produces a brighter flare. This asymmetry depends on the star’s speed, size, and disc density and could naturally explain the strong-weak brightness pattern observed in QPEs.

Za prenašanje predavanj v živo in snemanje preklapljamo iz Zooma na Youtube. Naša Youtube stran je https://www.youtube.com/@astroFMF, kjer lahko najdete stare posnetke in povezavo za ogled predavanja v živo.