Undergraduate Honors Theses

Thesis Defended

Spring 2015

Document Type


Type of Thesis

Departmental Honors



First Advisor

Philip Armitage

Second Advisor

Erica Ellingson

Third Advisor

Lonni Pearce


Modeling black hole X-ray binaries is complex in nature due to the complicated physical processes occurring in the disk (i.e., scattering, absorption and emission, relativistic effects); however, the overall effect is a relatively minor shift of the emergent spectrum towards harder energies. A single parameter, fcol is generally used to phenomenologically capture the global effect on the observed spectrum. A chi-square minimization routine was developed in order to fit three parameters to an accretion disk spectrum: a normalization constant, the maximum temperature of an accretion disk, and the spectral hardening factor fcol in an attempt to constrain fcol. However, a stronger parameter degeneracy than expected did not allow this to work. As a consequence, fcol was left as a constant, 1.0, and the algorithm successfully fit input disk spectra to my developed model by exploring combinations of N and Tmax. In order to further the research, I will employ Markov Chain Monte Carlo methods to better explore the parameter space and learn how the vertical disk structure, specificially the reprocessing of energy in the disk’s atmosphere, the corona, has an effect on the spectral hardening factor.