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Astrophysics, High Energy Astrophysical Phenomena, astro-ph.HE,General Relativity and Quantum Cosmology, gr-qc
Abstract:
We investigate the dynamics of a circumbinary disc that responds to the loss
of mass and to the recoil velocity of the black hole produced by the merger of
a binary system of supermassive black holes. More specifically, we perform the
first two-dimensional general relativistic hydrodynamics simulations of
\textit{extended} non-Keplerian discs and employ a new technique to construct a
"shock detector", thus determining the precise location of the shocks produced
in the accreting disc by the recoiling black hole. In this way we can study how
the properties of the system, such as the spin, mass and recoil velocity of the
black hole, affect the mass accretion rate and are imprinted on the
electromagnetic emission from these sources. In contrast with what done in
similar works, we here question the estimates of the bremsstrahlung luminosity
when computed without properly taking into account the radiation transfer, thus
yielding cooling times that are unrealistically short. At the same time we
show, through an approximation based on the relativistic analogue of the
isothermal evolution of \citet{Corrales2009}, that the luminosity produced can
reach a peak value above $L \simeq 10^{43} {\rm erg/s} $ at about $\sim 20 {\rm
d}$ after the merger of a binary with total mass $M\simeq 10^6 M_\odot$ and
persist for several days at values which are a factor of a few smaller. If
confirmed by more sophisticated calculations such a signal could indeed lead to
an electromagnetic counterpart of the merger of binary black-hole system.
