Date of Award

Summer 8-15-2018

Author's School

Graduate School of Arts and Sciences

Author's Department


Degree Name

Doctor of Philosophy (PhD)

Degree Type



Mass accreting stellar mass and supermassive black holes are strong sources of X-rays. The X- ray observations enable studies of the process of black hole accretion and give us information about the spacetime background. In the framework of my thesis work, I have continued the development of a general-relativistic ray-tracing code enabling the simulation of the Comptonization of photons in the hot accretion disk corona. I use the code to investigate the impact of various approximation schemes for modeling the Comptonization finding that a fully relativistic treatment is needed for accurate predictions in the soft and hard X- ray regimes (0.1-100 keV). I use the code to study the impact of the 3-D geometry of the corona on the observed X-ray flux and polarization energy spectra. Furthermore, I study the observational signatures of accretion disk hotspots orbiting the black holes. Such orbiting hotspots have been invoked to explain the presence of high-frequency quasi-periodic oscillations (HFQPOs) in the X-ray light curves from several accreting stellar-mass black holes. I use the newly developed numerical tools to model the properties of one supermassive black hole (Mrk 335) and one stellar mass black hole (GRS 1915+105). I conclude with a discussion of the scientific potential of spectral, timing, and polarimetric studies of black holes with missions such as the Imaging X-ray Polarimetry Explorer (IXPE) and the enhanced X-ray Timing and Polarimetry Mission (eXTP). As a graduate student, I played an active role in preparing the X-Calibur hard X-ray polarization mission for a long duration balloon flight from McMurdo in December 2018. My work aimed at reducing the readout noise of the polarimeterճ Cadmium Zinc Telluride (CZT) detectors. My work contributed to a substantially lower energy threshold and thus a substantially improved sensitivity of X- Calibur.


English (en)

Chair and Committee

Henric Krawczynski

Committee Members

Ramanath Cowsik, Martin H. Israel, Jon Miller, Zohar Nussinov,


Permanent URL: 2018-08-15