| Abstract: Accretion onto stellar-mass black holes in X-ray binaries drives a rich range of spectral and temporal phenomena across the electromagnetic spectrum. In particular, the ultraviolet (UV) and X-ray bands provide direct probes of the accretion disk, hot corona, and disk–wind interactions, making them crucial for understanding accretion dynamics. In this work, we investigate the accretion properties of black hole X-ray binaries through combined UV–X-ray spectral studies.
We utilise simultaneous and quasi-simultaneous observations from space-based UV and X-ray instruments, enabling broadband coverage from the outer accretion disk to the innermost regions near the black hole. The observed spectra are modelled using physically motivated broadband accretion models, incorporating thermal emission from the disk, Comptonization in the corona, and reprocessing and absorption by disk winds. This approach allows us to track the evolution of key accretion parameters—such as mass accretion rate, inner disk radius, coronal temperature, and optical depth—across different spectral states and luminosity regimes.
Our results demonstrate how UV emission constrains the outer disk structure and irradiation effects, while X-ray spectra probe the inner accretion flow and high-energy processes. By linking UV and X-ray properties within a unified theoretical framework, we provide new insights into state transitions, disk–corona coupling, and the role of outflows in black hole X-ray binaries. |
