Dartmouth Events

Abstract: Supermassive binary black holes in gaseous environments are key
multi-messenger sources for the LISA mission and pulsar timing arrays
as they are powerful emitters of light and gravitational waves.  Their
electromagnetic output relies on the accretion of gas onto the black
holes, one of the universe's most powerful and efficient processes for
converting mass into energy that is involved in such exotic
astrophysical phenomena as x-ray binaries, gamma-ray bursts, active
galactic nuclei, kilonova, and tidal disruption events. Simulating
these systems realistically is challenging as radiation-coupled
magnetohydrodynamics (MHD) must be considered over large dynamic
ranges in space and time.  We will provide a brief summary of the
progress made in our group to understand accreting binary black hole
systems theoretically using high-performance simulations of general
relativistic MHD and dynamic spacetimes. We will report what effect
the evolution duration, accretion disk size, and binary mass ratio
have on the structure and variability of the accretion flow. We
particularly emphasize how these parameters influence the over-density
feature which orbits the binary, since it is responsible for most of
the electromagnetic emission's variability---a key signature of the
system being a binary. Extending to smaller length scales, we will
report on simulations following accretion all the way down to the
event horizons so that we may begin to investigate how black hole spin
affects mini-disk dynamics, accretion rate, and jet power. We will
conclude by reporting on our radiative transfer predictions for how
black hole spin alters the spectral energy distribution of these
systems.

Hosted by Yi-Hsin Liu