Topic: tidal disruption events

Quasi-periodic eruptions are repeating X-ray transients from supermassive black holes in nearby low-mass galactic nuclei. Their regularity, timescales and energetics suggest stellar companions orbiting at about 100 gravitational radii. They may provide unusually close dynamical probes of black holes and electromagnetic counterparts to extreme mass-ratio inspirals, a target for future space-based gravitational-wave observatories such as LISA. Joheen Chakraborty reviews the thirteen known systems, including the unexpected appearance of several in accretion discs created by tidal disruption even

Shane Davis presents simulations of stellar disruption and the subsequent return of debris to a black hole. Observed light curves and spectra offer tests of accretion physics and black-hole spacetime, but interpreting them requires accounting for strong radiation forces during rapid fallback. Using Athena++ and AthenaK, the research models radiation transfer, including recent calculations in Kerr spacetime. Although the debris circularizes slowly, shocks involving the returning stream and an eccentric disk dominate early energy release and angular-momentum transport. Radiation drives unbound