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The accretion-ejection coupling in Galactic accreting black holes

PhD ceremony:Y. Zhang, Dr
When:September 26, 2023
Start:09:00
Supervisor:prof. dr. R.M. (Mariano) Mendez
Co-supervisor:dr. D. Altamirano
Where:Academy building RUG
Faculty:Science and Engineering
The accretion-ejection coupling in Galactic accreting black holes

During outburst, black-hole X-ray binaries (BHXRBs) exhibit time variability over a wide range of timescales from subseconds to years and wavelengths from radio to X-rays, offering a unique insight into the accretion-ejection processes and the underlying physics of these sources. Even if still being in its infancy, the modelling of the so-called quasi- periodic oscillations and the broadband noises, holds the promise to constrain the geometry of the accretion flow around BHs, especially the accreting corona that is believed to connect the accretion and the ejection zones. In the past decades, tremendous progress has been made in understanding the nature of the high-energy corona. However, many questions persist: What is the nature of the corona and how does its geometry evolve during the outburst? What is the role of the corona during the accretion-ejection process? Is the change of the time variability and spectral state determined by the appearance and disappearance of the corona? 

Using data from NICER and Insight-HXMT, Yuexin Zhang found that the geometry of the corona in MAXI J1535-571 evolved during its 2017 outburst. The comparison with the evolution of radio flux density further indicates a morphological coupling between the corona and the jet. Using data from RXTE, Zhang investigated the high-frequency (~ 70 Hz) broadband variability component in GRS 1915+105 and GX 339-4. This component, as a proxy, shows a radiative coupling between the corona and the jet.