Studying The Variabilities Of The Tidal Disruption Events And Associated Phenomena

A tidal disruption event (TDE) occurs when a star ventures close enough to a supermassive black holes (SMBH) in quiescent galaxies that its tidal force overcomes the star’s self-gravity. Swift J1644+57 is believed to be an TDE. As expected by theoretical analysis, the X-ray emission from Swift J1644+57 follow the standard behavior of t-5/3. However, a significant fluctuations are observed in the X-ray lightcurve. These fluctuations may provide an interesting clue to the nature of TDEs. My thesis mainly focuses on studying these fluctuations and attempts to give some explanation.It is interesting that the X-ray emission from Galactic X-ray black hole binaries (BHBs) and active galactic nuclei (AGNs) also shows significant aperiodic variability. As proposed by Lyubarskii (1997), the aperiodic variability is likely from the fluctuation of the disk viscous parameter. In the first chapter we broadly survey TDEs physics and observations. The second chapter shows our works and results about the light curve of TDEs. As performing power density spectra analysis on the fluctuations in the decaying phase of Swift J1644+57, we find the power of fluctuations can be described as P～f-1.2, which is similar to those found in BHBs and AGNs. Then we study the variability of accretion rate and jet power from the accretion disk in a TDE based on the propagating fluctuations model. The light curves and variabilities of jet power from a torus are obtained, and the power spectra density of the variabilities in the decaying phase is analyzed. Our result shows that the power of variabilities can be described as P～f-1.2, which is similar to be found in Swift J1644+57. It reveals that the mechanism deriving variabilities in BHBs and AGNs may be at work in Swift J1644+57. We also attempt to study the variabilities of the TDE with considering the behavior of fallback material. This work is still on the processing. In addition, we study the variabilities of jet power powered from a hyper-accretion disk. We find that the variabilities we get are similar to those of observations. The mechanism deriving variabilities in BHBs and AGNs may be at work in a hyper-accretion disk.