My research is concerned primarily with the high-energy realm of astrophysics, which deals with the most extreme environments encountered in the universe. Generally speaking, the extreme environment with which I work most is the region of space and time around a black hole -- an object so dense that not even light can escape its gravitational grasp.

Specifically, in collaboration with my previous advisor Mitch Begelman, I have developed a model for the manner in which the debris from a tidal disruption event, which occurs when a star is destroyed by the immense gravitational field of a black hole, surrounds and accretes onto the black hole that destroyed the original star. This ZEro-BeRnoulli Accretion, or ZEBRA, model states that the tidally-disrupted material conforms to a quasi-spherical envelope that surrounds the black hole. The continued accretion onto the black hole results in the launching of powerful, bipolar jets that escape from the system along the rotational axis of the envelope. The cartoon picture looks something like this (image credit: Michael Huber, mhuberproart@gmail.com): model

I’ve also been working on models that analyze the way in which the jets launched during tidal disruption events interact with their surrounding medium (the ZEBRA envelope). These radiation-viscous models, which assume that the transport of energy and momentum between the envelope and the jet acts locally between the radiation and massive particles, then prescribe specific density and velocity profiles for the outflow. The observational consequences of these models may then inform us of the properties of the black hole and the disrupted star.

Finally, I’ve also been working with Chris Nixon on the numerical modeling of tidal disruption events. We have been using PHANTOM, an SPH code developed by Dan Price, to account for the complicated hydrodynamical processes that take place during a realistic tidal disruption event. One of the biggest findings of our research is that the stream of debris produced from the disruption is gravitationally unstable, and it collapses into bound fragments that form at late times (see picture below, image credit: Steven Burrows, JILA). model

If you’d like to know more about these projects, please visit the publications page.

Collaborators: Mitch Begelman, Chris Nixon, Phil Armitage, Dan Price