I am interested in understanding the plasma that flows around black holes and neutron stars in our galaxy, as well as in enormous clusters containing thousands of galaxies.  In both settings the gas is heated to millions of degrees and emits most strongly in the X-ray part of the spectrum.

In the classic theory of accretion disks, when a companion star orbits too close to a black hole or neutron star it loses gas to a disk swirling around the dense compact star.  Time variability of the X-ray emission reveals turbulence and quasiperiodicity in the accretion disk.  I study the dynamics of these disks and the connections with the measurements of the X-ray variability.

Millions of times larger black holes reside in the centers of giant galaxies which themselves occupy the centers of huge clusters of galaxies.  Turbulent gas motions in such clusters regulate the feeding of supermassive black holes. What are the interactions between galaxies, gas, and black holes in these environments?