Exploring Coronal Structures Through X-Ray Polarimetry

Advisor: Michal Dovčiak (ASU CAS)

Funding: Fully funded

Website: https://astro.cas.cz/people/michal-dovciak

Contact: dovciak@asu.cas.cz

Black holes are extraordinary cosmic laboratories where gravity becomes so strong that even light struggles to escape. Yet, despite their invisibility, we can study them through the high-energy radiation produced by the matter spiraling into them. X-ray observations — especially the newest ability to measure X-ray polarization — allow us to probe the geometry, motion, and physical conditions of matter in the most extreme environments known. With modern missions now providing the first detailed polarimetric data, we are entering a period where long-standing questions about how accretion disks, coronae, and jets actually work can finally be addressed with entirely new diagnostics.

A student joining this project would have the opportunity to participate directly in these developments. Their primary focus would be on studying Comptonisation in various coronal geometries, with particular emphasis on both extended coronal structures and compact lamp-post–like configurations. As an additional step, they would also explore outflowing coronae and assess how bulk motion affects scattering and polarization. All final models will include full general relativistic effects — already present in the frameworks from which we will build — and will ultimately be applicable to real observations from the IXPE mission. Through this work, the student will directly contribute to advancing our understanding of how coronal structure and dynamics govern high-energy emission near black holes.

The PhD student will naturally collaborate with the other members of the well established Group of Relativistic Astrophysics at Astronomical Institute of Academy of Sciences: Jiří Svoboda, Michal Bursa, Jakub Podgorný and others.

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