A theoretical study of the time lags due to Comptonization and the constraints on the X-ray corona in AGNs

0570192 - ASÚ 2024 RIV GB eng J - Journal Article
Zhang, Wenda - Papadakis, I.E. - Dovčiak, Michal - Bursa, Michal - Karas, Vladimír
A theoretical study of the time lags due to Comptonization and the constraints on the X-ray corona in AGNs.
Monthly Notices of the Royal Astronomical Society. Roč. 519, č. 4 (2023), s. 4951-4965. ISSN 0035-8711. E-ISSN 1365-2966
R&D Projects: GA ČR(CZ) GA18-00533S
Grant - others:Ministerstvo školství, mládeže a tělovýchovy - GA MŠk(CZ) LM2018140
Institutional support: RVO:67985815
Keywords : black hole physics * active galaxies * X-rays
OECD category: Astronomy (including astrophysics,space science)
Impact factor: 4.8, year: 2022
Method of publishing: Limited access
https://doi.org/10.1093/mnras/stac3625

We study the Fourier time lags due to the Comptonization of disc-emitted photons in a spherical, uniform, and stationary X-ray corona, which located on the rotational axis of the black hole. We use MONK, a general relativistic Monte Carlo radiative transfer code, to calculate Compton scattering of photons emitted by a thin disc with a Novikov-Thorne temperature profile. We find that the model time lags due to Comptonization remain constant up to a characteristic frequency and then rapidly decrease to zero at higher frequencies. We provide equations that can be used to determine the time lags and cross-spectra for a wide range of values for the corona radius, temperature, optical depth, height, and for various accretion rates and black hole masses. We also provide an equation for the X-ray luminosity of a single corona, as a function of its characteristics and location above the disc. Remarkably, the observed X-ray time lags of nearby, bright active galaxies can be successfully reproduced by inverse Comptonization process of multiple dynamic coronae.
Permanent Link: https://hdl.handle.net/11104/0341975