Speaker
Description
A tidal disruption event (TDE) occurs when a star ventures too close to a massive black hole. Initially, the angular momentum of the star's orbit may not coincide with the black hole's spin axis, resulting in the formation of a tilted accretion disk relative to the black hole. The Lense-Thirring effect then sets this disk into precession. In this study, we have constructed a precessing super-Eddington TDE disk model, drawing on the outcomes of simulations. Using this model, we calculate the spectra from a range of viewing angles. As the disk precesses, the viewing angle changes over time, leading to a periodic evolution of the light curve. Our analysis demonstrates that the X-ray flux is highly variable, responding to the shifts in viewing angle caused by disk precession. In contrast, the optical and near-ultraviolet (NUV) emissions, which originate from the reprocessed material in the outflow, exhibit relatively less variability. We have identified three distinct regimes of variability driven by disk precession. Firstly, when the precession occurs within a narrow range of viewing angles, the light curve experiences only minimal modulations. Secondly, within a moderate range of viewing angles, intense X-ray variability is observed. This includes instances where X-rays disappear at viewing angles $\gtrsim 50^{\circ}$, and there is an inverse correlation between X-ray and optical/NUV emissions. Thirdly, when the precession spans an extremely wide range of viewing angles, substantial modulations are seen across both the X-ray and optical/NUV bands. For precession periods longer than one year, there is a possibility of late - time rapid X-ray brightening. This phenomenon could potentially account for the late-time X-ray activity observed in some TDEs. Our model offers a more profound understanding of the dynamics of precessing accretion disks and the underlying physics of TDEs.