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

The Milky Way is thought to be populated with ~10**3-10**4 stellar-mass black holes (BHs) that are fed by gas accreted from companion stars in tight orbits. Most of these BHs are transient and exhibit episodic X-ray outbursts on decadal timescales - the smoking gun that led to their discovery. However, since their duty cycles are very low, the vast majority remain hidden in a dormant state, awaiting to be discovered. Here I present the current census of such transient BH X-ray binaries, summarize their observed properties and discuss new avenues to increase the size of the known population.

Location: ASU Spořilov, seminar room 101

remote online connection possible via: https://us02web.zoom.us/j/3464248686

We are made of stardust—or, at least in significant parts, of material processed in stars. Hot, massive giant stars can drive the chemical evolution of galaxies and trigger and quench star formation through their strong winds and their final demise as supernovae. Yet optical and X-ray measurements of the wind mass loss strongly disagree and can only be reconciled if the winds are highly structured, with colder, dense clumps embedded in a tenuous hot gas. In (quasi-)single stars, however, wind properties are inferred for the whole wind ensemble only; no measurements of individual clumps or clump groups are possible, limiting our understanding of wind properties and launching and therefore of massive stars themselves. Luckily, nature provides us with perfect laboratories to study clumpy winds: high mass X-raybinaries. The radiation from close to the compact object is quasi-point like and effectively X-rays the wind, in particular the clumps crossing our line of sight. In this talk, I will discuss how we can use a variety of observations to constrain the wind properties in bright high mass X-ray binaries in particular focussing in advances from recent ears as done by the X-wind collaboration. Time- and absorption-resolved high resolution X-ray spectroscopy reveals the composition of the multicomponent wind plasma, the structure of the accretion wake, and the wind's response to changes in irradiation. New simulations of wind accretion pave the way towards constraining clump properties from stochastic variability of absorption. New X-ray telescopes such as XRISM and future instruments such as NewAthena will revolutionise the field, allowing us to observe individual clumps in bright sources and, for the first time, make faint sources accessible for high resolution spectroscopy.

Location: seminar room 101

remote online connection possible via: https://us02web.zoom.us/j/3464248686

Active Galactic Nuclei (AGN) are an essential component of current theories of galaxy evolution. Specifically, the energy released by material accreting onto the central supermassive black hole (SMBH) is believed to generate outflows which suppress star formation throughout the host galaxy. However, the mechanisms by which activity in the central parsecs of a galaxy impacts gas thousands of times further away is poorly understood. To better understand the physics of "AGN feedback," and its various manifestations, we have begun a multi-scale, multi-wavelength investigation of AGN outflows in a sizable and diverse sample of relatively nearby galaxies. In this talk, I will discuss this project and present our initial findings -- including a "bonus" discovery of the interaction between an AGN jet and a satellite galaxy.

Location: ASU Praha-Spořilov

There is ample evidence that supermassive black holes (SMBHs) exist in the nuclei of all massive galaxies and that the masses of the SMBHs scale with properties of their host galaxies, e.g. stellar velocity dispersion (M_BH - σ*), bulge mass (M_BH - M_Bulge), and stellar mass (Μ_ΒΗ - Μ_*). These scaling relations are believed to be the result of co-evolution between the SMBH and its host galaxy. However, the situation in low mass and dwarf galaxies is less clear, with large uncertainties in both the occupation fraction and scaling relations. In addition, if the relations hold true, low mass galaxies should host intermediate mass black holes (IMBHs). Understanding black holes in low mass galaxies is crucial for understanding galaxy evolution, formation of seed black holes in the early universe, and the search for IMBHs. In this talk I will discuss the low mass end of the BH-galaxy scaling relations and search for IMBHs with a focus on a peculiar galaxy, IC 750, a near-by low mass galaxy. I will present a multi-wavelength study of IC 750 which shows that it hosts a 1 x 10^5 M_sun black hole which is undermassive by one to two orders of magnitude below the BH-galaxy scaling relations. I will also show results on the accretion processes in the system and summarize searches for other such systems. I will conclude with the implications of these results on theories of BH-galaxy co-evolution and future prospects.

Location: ASU Praha-Spořilov

TBD

Location: GPS/Sporilov

TBD

Location: ASU Sporilov, 101