Dissertation defence (Astronomy): MSc Vadzim Krautsou
Time
12.12.2025 12.00 – 16.00
MSc Vadzim Krautsou defends the dissertation in Astronomy titled “Polarized Radiation from Accreting Black Holes in X-Ray Binaries” at the University of Turku on 12 December 2025 at 12.00 (University of Turku, Turku School of Economics, Lähitapiola lecture hall, Rehtorinpellonkatu 3, Turku).
Opponent: Professor Andrew Shearer (University of Galway, Ireland)
Custos: Professor Juri Poutanen (University of Turku)
Doctoral Dissertation at UTUPub: https://www.utupub.fi/handle/10024/194400
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Summary of the Doctoral Dissertation:
When a massive star reaches the end of its life, it collapses and becomes one of the most fascinating cosmic objects – a black hole, whose gravity is so strong that not even light can escape it.
Roughly a third of all stars in our Galaxy form binary systems, which means that over time, many evolve into pairs where one star remains alive while the other has already turned into a black hole. If the black hole is close enough to its companion, it begins to strip matter from it, heating it to millions of degrees in a process known as accretion. During accretion, enormous amounts of energy are released as radiation, which we can detect with telescopes across different wavelengths.
In my dissertation, I use the data from various ground- and space-based telescopes to study how accreting black holes emit light. In particular, I investigate the polarization of their radiation – the orientation in which light waves oscillate as they travel. Polarization reveals information about the geometry and physical properties of the regions the emission originates.
Recent advances in instrumentation, such as the optical polarimeters DIPol-2 and DIPol-UF, as well as the launch of the Imaging X-ray Polarimetry Explorer (IXPE) satellite, have for the first time made it possible to measure polarization from black hole systems in both optical and X-ray ranges with unprecedented precision. These observations provide new insights into the physics of matter under extreme conditions near black holes – conditions that cannot be reproduced in any laboratory on Earth.
Opponent: Professor Andrew Shearer (University of Galway, Ireland)
Custos: Professor Juri Poutanen (University of Turku)
Doctoral Dissertation at UTUPub: https://www.utupub.fi/handle/10024/194400
***
Summary of the Doctoral Dissertation:
When a massive star reaches the end of its life, it collapses and becomes one of the most fascinating cosmic objects – a black hole, whose gravity is so strong that not even light can escape it.
Roughly a third of all stars in our Galaxy form binary systems, which means that over time, many evolve into pairs where one star remains alive while the other has already turned into a black hole. If the black hole is close enough to its companion, it begins to strip matter from it, heating it to millions of degrees in a process known as accretion. During accretion, enormous amounts of energy are released as radiation, which we can detect with telescopes across different wavelengths.
In my dissertation, I use the data from various ground- and space-based telescopes to study how accreting black holes emit light. In particular, I investigate the polarization of their radiation – the orientation in which light waves oscillate as they travel. Polarization reveals information about the geometry and physical properties of the regions the emission originates.
Recent advances in instrumentation, such as the optical polarimeters DIPol-2 and DIPol-UF, as well as the launch of the Imaging X-ray Polarimetry Explorer (IXPE) satellite, have for the first time made it possible to measure polarization from black hole systems in both optical and X-ray ranges with unprecedented precision. These observations provide new insights into the physics of matter under extreme conditions near black holes – conditions that cannot be reproduced in any laboratory on Earth.
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