We investigate evolution of an accretion disc in binary black hole ( BBH ) systems and possible electromagnetic counterparts of the gravitational waves from mergers of BBHs .
Perna et al .
( 2016 ) proposed a novel evolutionary scenario of an accretion disc in BBHs in which a disc eventually becomes ‘ ‘ dead ’ ’ , i.e. , the magnetorotational instability ( MRI ) becomes inactive .
In their scenario , the dead disc survives until a few seconds before the merger event .
We improve the dead disc model and propose another scenario , taking account of effects of the tidal torque from the companion and the critical ionization degree for MRI activation more carefully .
We find that the mass of the dead disc is much lower than that in the Perna ’ s scenario .
When the binary separation sufficiently becomes small , the mass inflow induced by the tidal torque reactivates MRI , restarting mass accretion onto the black hole .
We also find that this disc ‘ ‘ revival ’ ’ happens more than thousands of years before the merger .
The mass accretion induced by the tidal torque increases as the separation decreases , and a relativistic jet could be launched before the merger .
The emissions from these jets are too faint compared to GRBs , but detectable if the merger events happen within \lesssim 10 Mpc or if the masses of the black holes are as massive as \sim 10 ^ { 5 } M _ { \odot } .