Fast variability in accretion systems research group


We are interested in fast stochastic variability (the so called flickering) generated by accretion process in cataclysmic variables. Mainly those with disc interest us. This dynamic photometric behaviour brings all informations about the accretion geometry and individual substructures of the flow. The most exciting is the very central region close to the central compact star radiating in X-rays. For this research we use optical data taken by Kepler satelite (example) and X-ray observatory XMM-Newton (example). We search for characteristic frequencies in the light curves with the goal to localise the physical source of the variability (example). For the latter we distinguish radiation source and the original fluctuation source, i.e. a mass accretion fluctuation generated at the outer accretion disc propagates inwards and liberates radiation at the inner disc boundary.

Our team is very signal oriented. Besides flickering we are interested in periodic or quasiperiodic oscillations in short satellite light curves with all the periodogram artifacts (example). Monte Carlo simulations are very usefull here (example). We collaborate with our partners on novae variability and we use data from XMM-Newton and Chandra (example). The goal is to identify spin of the white dwarf or pulsations in the hydrogen burning layer. The periodograms are sometimes very complicated and various effects produce annoying artifacts (example). Such problematic periodogram can yield to wrong interpretation.


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As cataclysmic variables are accretion powered systems like X-ray binaries or AGNs, we do not refuse to look farther. We started to analyse fast variability of AGNs present in the Kepler field in order to search for multicomponent nature of the flickering (example). Swift X-ray data were also very useful in this case. So far we studied instrumental effects strongly contaminating AGN observations by Kepler (example).


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Our team is supported by ESA project "PREPARATION FOR ATHENA MISSION BY ESTABLISHING SLOVAK RESEARCH TEAM X-RAY MISSIONS AND AGN STUDY". During the first year (started 01.03.2019) we will increase our skills in XMM-Newton, Chandra, Swift and NuSTAR observations. The second year will be dedicated to increasing our knowledge of AGN phenomenology and physics. The project realisation will be based on experts visits and workshops. We will complete the project by a final workshop or small conference.


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Majority of our team is oriented more to IT technologies, rather than physics. This is based on the character of the host faculty. We have ambition to offer databaze, scripting, automation support for satellite observations to Slovak astronomical comunity. For now, if you need to extract basic products from XMM-Newton, Chandra, Swift, Kepler or NuSTAR archive, we could help. Moreover, recently we start to study and (try to) apply machine learning to astronomical research. We welcome any scientific suggestion or inspiration, but please be patient. We need time...


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Pavol Bezák      researcher, signal analysis, periodic variability, satellite archives and basic products extraction (XMM-Newton)
Dominika Janíková      researcher, satellite archives and basic products extraction, satellite archives and basic products extraction (Swift, TESS)
Denis Benka      PhD student, signal analysis, stochastic variability, satellite archives and basic products extraction (NuSTAR)
Jozef Magdolen      PhD student, signal analysis, periodic/quasiperiodic variability, satellite archives and basic products extraction (Chandra)
Sabína Vašová      undergraduate student, working on light curve classification using convolutional neural networks (diploma thesis)
Ivan Latkóczy      undergraduate student, working on software for rms-flux analysis (bachelor thesis)
Andrej Dobrotka       scientific leader, astrophysicist (This email address is being protected from spambots. You need JavaScript enabled to view it.)


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Advanced Technologies Research Institute
Faculty of Materials Science and Technology in Trnava
Slovak University of Technology in Bratislava
Jána Bottu 8857/25
917 24 Trnava
GPS:  48.37088 17.572509

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