Research Areas

The Event Horizon Telescope

The Event Horizon Telescope (EHT) is an experiment that is being performed on a large and ever-increasing array of radio telescopes that span the Earth from Hawaii to Chile and from the South Pole to Greenland. Its goal is to study black holes through imaging at very high spatial resolution. The main goal of the EHT is to image the event horizons of supermassive black holes, with an unprecedented 10-microarcsecond resolution.

Neutron Stars and their Interiors

The nature and interactions of matter at high densities and low temperatures is one of the great unsolved problems in modern science, with profound implications for particle physics and astrophysics. Neutron star cores contain the densest matter known in the Universe, and therefore, determining their properties provides a direct way of measuring the equation of state of ultra dense matter. I work on the surfaces of neutron stars and on the development of spectroscopic methods to measure neutron star radii with increasing precision. I also focus on the optimal ways to infer the neutron star equation of state from these measurements. Furthermore, I develop new statistical tools to extract the measurements and uncertainties from large data sets.

NICER

One of the most significant developments in the measurement of the dense matter equation of state is going to come from the NICER detector, built as an astrophysics payload that arrived on the International Space Station in 2017. Instead of focusing on spectroscopy, NICER will take a very different approach to measuring neutron star radii, based on the shapes and amplitudes of the pulsed emission observed from neutron star surfaces in multiple wavebands. Because of light bending effects in general relativity, these waveforms encode information about the neutron star space-time, and therefore, its radius and mass. We work on the most sophisticated calculations of these waveforms and methods, similar to image reconstruction and Doppler tomography, for extracting radius information from the upcoming data. We are currently applying these techniques to the pulsars that NICER has observed.

LYNX

Lynx is the high-energy flagship mission concept funded for study by NASA for consideration in the 2020 Astrophysics Decadal Survey.

High Performance Computing
Rendering time-dependent images of black holes in order to study their horizons and accretion flows and radiation transport in spinning neutron star space times are highly complex problems that require fast, efficient, large-scale algorithms for their solutions. My research group specializes in the development and application of such algorithms on the GPU platform. GPUs were first developed for highly parallelizable applications such as computer games that required fast, high resolution image rendering. We are one of the very few groups who pioneered their use for problems in astrophysics and the efficiency they are enabling is bringing about a revolution.