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

0538501 - ASÚ 2021 RIV FR eng J - Článek v odborném periodiku
Ursini, F. - Dovčiak, Michal - Zhang, Wenda - Matt, G. - Petrucci, P. O. - Done, C.
Estimating the size of X-ray lamppost coronae in active galactic nuclei.
Astronomy & Astrophysics. Roč. 644, December (2020), č. článku A132. ISSN 0004-6361. E-ISSN 1432-0746
Grant CEP: GA ČR(CZ) GA17-02430S
Institucionální podpora: RVO:67985815
Klíčová slova: black hole physics * active galaxies * X-rays
Obor OECD: Astronomy (including astrophysics,space science)
Impakt faktor: 5.803, rok: 2020
Způsob publikování: Omezený přístup
https://doi.org/10.1051/0004-6361/202039158

We 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.
Trvalý link: http://hdl.handle.net/11104/0316294