In my research I am focussing on the following topics (keep scrolling down for more details):

  • Polarized radiative transfer
  • Gravitational Waves
  • GRMHD simulations of accretion onto compact objects: Disks and jets
  • Electromagnetic counterparts to GW sources: Circumbinary accretion disks
  • Numerical Relativity

Polarized radiative transfer

Models for the Event Horizon Telescope with Prof. Jonathan McKinney I am studying the physics of black hole accretion disks using the grmhd code HARM as well as the effects of polarized radiative transfer. Polarization measurements of the innermost regions in our galactic center Sag A* and the nearby giant-elliptical galaxy M87 with the Event Horizon Telescope may provide key data to distinguish between competing accretion disk models.

Collaborators:
Jonathan C. McKinney, Michael D. Johnson, Sheperd S. Doeleman

Gravitational Waves

A significant part of my work consists of modeling strong gravitational wave sources, which have been detected directly by the ground-based interferometer advanced LIGO. There is now good reason to belief that such detection will become routine over the next 1-2 years. In the longterm signals from supermassive black hole binaries will be detected by Pulsar Timing Arrays, and (future) space-based missions (LISA). One of the many great things about gravitational waves is that they are generated only in the most violent events in the universe but once emitted they pass through everything essentially without any interaction and are therefore excellent, clean probes of strong-field gravity.


Collaborators:
Bernd Bruegmann, Sebastiano Bernuzzi, Frans Pretorius, Marcus Thierfelder, Vasileios Paschalidis, Milton Ruiz, Stuart L. Shapiro, Zachariah B. Etienne, Harald P. Pfeiffer

GRMHD simulations:
Accretion onto single and binaries of compact objects

Accretion onto black holes is by far the most efficient process to convert mass into outgoing radiation. Accreting supermassive black holes (eventhough "only" of roughly solar system size) can outshine their entire host galaxy. Many theoretical ideas have emerged over the last 4 decades and is met by an increasing amount of observational data across the EM spectrum. In my work I contribute to the challenge of finding the connection between some theoretical ideas to what is observed in our universe. For this purpose it is necessary to solve the set of magnetohydrodynamic equations in the framework of General Relativity. In order to capture the full, non-linear and highly dynamic behavior, large scale, numerical simulations are required.
Collaborators:
Vasileios Paschalidis, Milton Ruiz, Stuart L. Shapiro, Zachariah B. Etienne, Harald P. Pfeiffer
Image credit: IL REU team: Sean E. Connelly, Abid Khan, Lingyi Kong, Brian R. Taylor, Stuart L. Shapiro

Electromagnetic counterparts to GW sources: Circumbinary accretion disks

I am studying the evolution of black hole binary system immersed in a magnetized gaseous disk. Due to the loss of orbital energy and angular momentum to gravitational waves the binary orbit decays, eventually leaving the disk behind, and leading to a merger into one black hole remnant. This leads to a strong perturbation of the inner disk and causes both strong gravitational wave and electromagnetic signatures. A simultaneous detection of both of these signals would provide a wealth of insights.


Collaborators:
Vasileios Paschalidis, Milton Ruiz, Stuart L. Shapiro, Zachariah B. Etienne, Harald P. Pfeiffer

Numerical Relativity: Eccentric binaries

During my Phd work with Prof. Bernd Bruegmann at the FSU Jena (Germany) I have worked on solving Einstein's Field equations on supercomputers for the inspiral and merger of compact object binaries. As part of my Phd work, I have studied the dynamics and gravitational wave signals of eccentric neutron star binaries as well as black hole binaries including "zoom-whirl" orbits.


Collaborators:
Bernd Bruegmann, Sebastiano Bernuzzi, Frans Pretorius, Marcus Thierfelder