Speaker
Description
Quasi-periodic eruptions (QPEs) are a recently discovered class of repeating X-ray flares from galactic nuclei hosting supermassive black holes. Their physical origin remains uncertain, but repeated collisions between a star and an accretion disc have emerged as a promising explanation. In this scenario, each disc crossing drives shocks, launches dense outflows, and produces radiation that may power the observed flares. We use three-dimensional radiation-hydrodynamics simulations to study the collision dynamics, the outflow properties, and the resulting radiative signatures. The simulations show that the interaction is naturally asymmetric: energy and momentum are redistributed preferentially along the star’s direction of motion, producing forward and backward outflows with different masses, velocities, and luminosities. The outflow and emission also depend on the stellar velocity and size, the disc density profile, and the inclination of the stellar orbit relative to the disc. Overall, these results support star-disc collisions as a promising framework for explaining the main observed features of QPE sources.