Multiwavelength study of accreting black holes in X-ray Binaries (Ph.D. Thesis discussion)
Maïmouna Brigitte
Black hole X-ray binaries are key laboratories for studying accretion physics and strong-field gravity. As matter is transferred from a donor star to the black hole, it forms a hot, rotating accretion disk that emits intense X-ray radiation. During outbursts, these systems brighten dramatically and evolve through distinct accretion states. Yet, their accretion geometry and wind structure remain poorly constrained. This thesis investigates accretion and emission processes in X-ray binaries using high-resolution spectroscopy, X-ray timing analysis, and polarimetry. Optical spectroscopy of the high-mass X-ray binary Cygnus X-1, obtained with the 2m Perek telescope, separates the donor star’s photospheric contribution from its stellar wind. The results reveal a clumpy wind with clear dependence on orbital phase and accretion state, and a strong anti-correlation with X-ray emission from the accretion disk. Timing analysis of the low-mass X-ray binary Swift J1727 identifies quasi-periodic oscillations during a rare soft-to-hard spectral transition, tracing variability propagation through the accretion flow at low luminosity. Finally, X-ray polarimetry of five systems constrains coronal geometry, with one source showing signatures consistent with strong-gravity light bending. Together, these results provide new constraints on wind–disk coupling, coronal structure, and accretion geometry in black hole X-ray binaries through a multi-wavelength approach.
Location: Faculty of Mathematics and Physics (room M252), Ke Karlovu 3, Praha 2