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arXiv · 2212.02734

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

W. Zhang·I. E. Papadakis·M. Dovčiak·M. Bursa·V. Karas
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Abstract

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 which 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 the 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.

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W. Zhang, I. E. Papadakis, M. Dovčiak, M. Bursa, V. Karas. 2022-12-06. A theoretical study of the time-lags due to Comptonization and the constraints on the X-ray corona in AGN. https://doi.org/10.1093/mnras%2Fstac3625

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