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Estimating the size of X-ray lamppost coronae in active galactic nuclei

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    SYSNO ASEP0538501
    Document TypeJ - Journal Article
    R&D Document TypeJournal Article
    Subsidiary JČlánek ve WOS
    TitleEstimating the size of X-ray lamppost coronae in active galactic nuclei
    Author(s) Ursini, F. (IT)
    Dovčiak, Michal (ASU-R) RID, ORCID
    Zhang, Wenda (ASU-R) ORCID
    Matt, G. (IT)
    Petrucci, P. O. (FR)
    Done, C. (GB)
    Article numberA132
    Source TitleAstronomy & Astrophysics. - : EDP Sciences - ISSN 0004-6361
    Roč. 644, December (2020)
    Number of pages9 s.
    Publication formOnline - E
    Languageeng - English
    CountryFR - France
    Keywordsblack hole physics ; active galaxies ; X-rays
    Subject RIVBN - Astronomy, Celestial Mechanics, Astrophysics
    OECD categoryAstronomy (including astrophysics,space science)
    R&D ProjectsGA17-02430S GA ČR - Czech Science Foundation (CSF)
    Method of publishingLimited access
    Institutional supportASU-R - RVO:67985815
    UT WOS000599907300002
    EID SCOPUS85097865420
    DOI10.1051/0004-6361/202039158
    AnnotationWe report estimates of the X-ray coronal size of active galactic nuclei in the lamppost geometry. In this commonly adopted scenario, the corona is assumed for simplicity to be a point-like X-ray source located on the axis of the accretion disc. However, the corona must intercept a number of optical/UV seed photons from the disc consistent with the observed X-ray flux, which constrains its size. At least for the sources accreting below the Eddington limit, we find that a Comptonizing lamppost corona can generally exist, but with constraints on its size and height above the event horizon of the black hole depending on the spin. For a maximally spinning black hole, a solution can almost always be found at any height, while for a non-spinning black hole the height must generally be higher than 5 gravitational radii. This is because, for a given luminosity, a higher spin implies more seed photons illuminating the corona, which is due to a larger and hotter inner disc area. The maximal spin solution is favoured, as it predicts an X-ray photon index in better agreement with the observations.
    WorkplaceAstronomical Institute
    ContactRadka Svašková, bibl@asu.cas.cz, Tel.: 323 620 326
    Year of Publishing2021
    Electronic addresshttps://doi.org/10.1051/0004-6361/202039158
Number of the records: 1  

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