Stream evolution in tidal disruption events

Tidal disruption events occur when a star gets scattered on a trajectory that takes it so close to a supermassive black hole that it is torn apart by strong tidal forces. Such events represent unique probes of otherwise quiescent black holes, which constitute the majority of black holes in the local universe. However, this great potential is hampered by the lack of a clear picture of how exactly these events take place. One particular uncertainty concerns the circularization process during which the stellar debris dissipate their large orbital energy to form an accretion disc around the black hole. Hydrodynamical simulations point towards shocks driven by debris self-intersections as an efficient dissipation mechanism. In my talk, I will present a recently developed semi-analytical model that treats the circularization process, accounting for the impact of both shocks and magnetic stresses. This model proves that the net effect of magnetic stresses is to strengthen shocks, thus accelerating circularization. It also allows to predict the form of the lightcurve associated to shock luminosity and demonstrates that the thermal energy excess imparted by shocks is most likely to cause the rapid formation of a thick structure. To conclude the talk, I will present latest advances on ongoing projects and mention future research directions.

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