I study accreting supermassive black holes, from the corona and inner disk to the gas that obscures them. I also help run the science operations of NuSTAR, build the upcoming UVEX mission, and shape future mission concepts.
How the X-ray corona heats the accretion disk and drives the ultraviolet and optical variability we see in active galactic nuclei. I develop the physical models that turn these delayed echoes into a picture of the innermost accretion flow.
XRISM now resolves the iron lines in active galactic nuclei finely enough to separate the gas moving at different speeds around the black hole. I use this to map the inner disk, the broad-line region, and the obscuring gas that earlier telescopes blurred together.
Since 2021, IXPE has let us measure the polarization of X-rays from active galactic nuclei, a completely new handle on the geometry of the innermost regions. I use it to work out where the X-rays come from and how much of what we see is reflection off the disk.
When X-rays reflect off the inner edge of the accretion disk, they carry the fingerprint of how fast the black hole spins. I study how to read that fingerprint, and when the standard methods can be trusted to give the right answer.
A lot of black holes are hidden behind thick gas and dust, and that gas is often on the move. I use hard X-rays to see through it, and passing clouds that briefly eclipse the source to measure how the obscuring material is arranged.
Most of what we know about black hole coronae comes from nearby, modest galaxies. I push the same measurements out to the brightest quasars in the universe, to test whether the physics we worked out locally still holds at the extremes.
The science a telescope can do is decided long before it launches. I help run today's X-ray missions and prepare the next generation, working out how to squeeze the most physics out of each new instrument.