Binary Black Hole Accretion

Binary black hole mergers in the presence of gaseous accretion flows are prime candidates for simultaneous observations of both gravitational waves and electromagnetic signals. I will present the results of 2D hydrodynamical simulations of circumbinary disk accretion using the moving-mesh code DISCO. These simulations demonstrate that gas accretion is not impeded by binarity. Gas is efficiently stripped from the inner edge of the circumbinary disk and enters the cavity along accretion streams, which feed persistent "mini-disks" surrounding each black hole. I will discuss characteristic periodicity in the measured accretion rate onto each BH, with implications for the quasar PG 1302-102 which shows recently reported evidence for periodic variability, as well as the dependence of the accretion flow on the binary mass ratio. I will also discuss characteristic modifications to the predicted spectrum which arise from shock heated gas inside the circumbinary cavity. Finally, I will discuss simulations which include binary inspiral and merger due to gravitational wave emission in order to track the changes in accretion and electromagnetic radiation as the orbit shrinks.

Speaker: Andrew MacFadyen (New York University)