The tidal disruption event by a supermassive black hole in Swift J1644+57 can trigger limit-cycle oscillations between a supercritically accreting X-ray bright state and a subcritically accreting X-ray dim state .
Time evolution of the debris gas around a black hole with mass M = 10 ^ { 6 } { \MO } is studied by performing axisymmetric , two-dimensional radiation hydrodynamic simulations .
We assumed the \alpha -prescription of viscosity , in which the viscous stress is proportional to the total pressure .
The mass supply rate from the outer boundary is assumed to be { \dot { M } } _ { supply } = 100 L _ { Edd } / c ^ { 2 } , where L _ { Edd } is the Eddington luminosity , and c is the light speed .
Since the mass accretion rate decreases inward by outflows driven by radiation pressure , the state transition from a supercritically accreting slim disk state to a subcritically accreting Shakura-Sunyaev disk starts from the inner disk and propagates outward in a timescale of a day .
The sudden drop of the X-ray flux observed in Swift J1644+57 in August 2012 can be explained by this transition .
As long as { \dot { M } } _ { supply } exceeds the threshold for the existence of a radiation pressure dominant disk , accumulation of the accreting gas in the subcritically accreting region triggers the transition from a gas pressure dominant Shakura-Sunyaev disk to a slim disk .
This transition takes place at t~ { } { \sim } ~ { } 50 / ( { \alpha } / 0.1 ) ~ { } { days } after the X-ray darkening .
We expect that if \alpha > 0.01 , X-ray emission with luminosity \gtrsim 10 ^ { 44 } { erg } { \cdot } { s } ^ { -1 } and jet ejection will revive in Swift J1644+57 in 2013–2014 .