Xiaoshan Huang (Caltech): "Pre-Peak Emission in TDEs"

The tidal disruption of a star by a nearby blackhole can power a bright flare in multiple wavebands, making a class of well-recognized transient events. Understanding the origin of detected emission from such tidal disruption events (TDEs) is particularly interesting. In this talk, I will discuss pre-peak emission mechanisms in TDEs with series of 3D radiation hydrodynamical (RHD) simulations. We found during stream-stream collision, enhanced radiation pressure can drive strong, optically-thick outflow, and the collision can happen multiple times. The following gas dynamics depends on the strength of the collision. In the limit of strong collision, the outflow may deplete gas near the blackhole, significantly delaying circularization or accretion. In weaker collisions, the circularization may still be delayed by outflow but will eventually concentrate gas near the orbital plane with reduced eccentricity, forming a radiation dominated accretion flow. The photosphere of such a pre-peak TDE system is likely to be anisotropic, either assembled by the optically thick outflow or early circularization gas. Post-processing the RHD simulations, the broad band spectrum from simulation favors a viewing-angle related effect to explain multi-band emission. We also address the importance of including atomic opacity in TDE radiation transfer calculations.