Theoretical and observational study of tidal disruption events

  A tidal disruption event (TDE) occurs when a star is stripped into pieces due to the tidal force that exceeds the star's self-gravity. TDEs provide an excellent opportunity to study the accretion phenomenon. We have constructed a time-dependent self-similar solution (models A and B) for an accretion disk with a general viscosity prescription that has a power law dependence on the radius, the density and the pressure for TDEs. The model A has a thin disk approximation with a polytropic pressure. The model B has a more general solution having a thick disk structure. The time evolution of luminosity in model A is faster than in model B, however, the maximum luminosity is higher for model B. I will also report the dependence of luminosity on the onset time of accretion and the corresponding disk outer radius. Besides, we have studied the spectral behaviour of TDEs using luminosity in UV (2500 angstrom) and X-ray (2 keV) bands observationally and theoretically. The spectral behaviour of TDEs for the observed TDE candidates ASAS-SN 14li, ASAS-SN 15oi, and XMM-SL1 are similar to the soft state in X-ray binaries (XRBs) and active galactic nucleus (AGNs) indicating that the black hole accretion is likely scale invariant. I will also present the study on spectral behaviour using various steady and time-dependent accretion models.