Tidal Disruption Events

Tidal Disruption Events (TDEs)

Tidal Disruption Events (TDEs) are violent disruptions of stars as a result of large tidal forces induced by extremely dense objects such as black holes and neutron stars. When a star gets disrupted, the tidal forces overcome the gravitational forces holding the star together. Due to the interaction between these forces, the star will be ripped apart. A fraction of the stellar material will be bound to the black hole. The remaining fraction of the material is unbound (left panel). The bound material can fall back to the Super Massive Black Hole (SMBH) and form an accretion disc (middle panel). For super-Eddington accretion rates, radiatively driven winds are expected to be launched, powered by the fallback material (right panel). These two components can generate large luminous flares that can be detected. Each component introduces a different time dependency into the lightcurve which we have analytically investigated.

Schematic view of the different phases of a TDE

Lightcurves

We have analytically derived the luminosity coming from the disc and wind component as a function of the properties of the star and SMBH involved in the event. Combining this with the numerical accretion rates obtained by Lodato et al. (2009) we have obtained new full light curves in three frequency bands. The wind component was found to be a dominant source of luminosity in the first 1000 days after disruption. This is indicative of a super-Eddington accretion rate after the initial formation of the accretion disc.

In the figure on the right the lightcurves from a disruption of a solar type star by a SMBH of a million solar masses. The solid line indicates the luminosity coming from the accretion disc with the dashed line signifying the luminosity from the wind and accretion disc together. This figure was featured in Roth et al. (2020). We improved the understanding of how the physical parameters affect the lightcurves. Furthermore, we showed that the wind component is dominant at early times, which was previously underestimated.