X-ray Comptonization in an Accreting Kerr Black Hole System with a Tilted Disc and Thermal Corona; A General-Relativistic Monte Carlo Simulation: I. Model, Radiative Transfer and Spectral-Timing Properties
Abstract
Quasi-periodic oscillations (QPOs) in the X-ray emission of accreting black hole binaries are commonly attributed to the relativistic Lense--Thirring precession of the inner accretion flow, in which a hot inner flow, tilted with respect to the black hole spin axis, precesses as a solid body while a cooler outer disc remains at its own, different tilt -- a warped, Bardeen--Petterson-type geometry. Testing this picture requires a radiative-transfer model that self-consistently follows photons through such a system: from emission near the innermost stable circular orbit (ISCO), through Compton scattering in a hot corona, to possible reflection off the misaligned outer disc, all under the full effects of light bending in Kerr spacetime. In this first paper of a two-part series, we present a general-relativistic Monte Carlo (GRMC) radiative-transfer model of a misaligned, warped, two-zone accretion system around a Kerr black hole. We describe the disc--corona geometry, the seed-photon prescription, the photon-transport engine -- including the geodesic integration scheme, the coronal Compton-scattering module and the outer-disc reflection treatment -- and the observer pipeline used to construct energy spectra, photon path-length and arrival-time distributions. We present the resulting energy spectra, light curves and spectral lags as functions of the black hole mass, corona size, outer-disc geometry, reflection albedo, photon-injection radius and observer inclination, and show how gravitational light bending systematically lengthens the path-length and arrival-time distributions of the escaping radiation. This model and its spectral-timing predictions form the foundation for Paper II, which extends the framework to track the full photon polarization state and presents the resulting energy- and precession-phase-resolved polarimetric signatures.
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BibTeX
@misc{chatterjee2026xray,
title = {{X-ray Comptonization in an Accreting Kerr Black Hole System with a Tilted Disc and Thermal Corona; A General-Relativistic Monte Carlo Simulation: I. Model, Radiative Transfer and Spectral-Timing Properties}},
author = {Mainak Chatterjee and Dipankar Bhattacharya},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.26769},
eprint = {2610.26769},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.26769},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - X-ray Comptonization in an Accreting Kerr Black Hole System with a Tilted Disc and Thermal Corona; A General-Relativistic Monte Carlo Simulation: I. Model, Radiative Transfer and Spectral-Timing Properties
AU - Mainak Chatterjee
AU - Dipankar Bhattacharya
PY - 2026
DA - 2026/10/19
PB - arXiv
DO - 10.48550/arxiv.2610.26769
UR - https://arxiv.org/abs/2610.26769
AB - Quasi-periodic oscillations (QPOs) in the X-ray emission of accreting black hole binaries are commonly attributed to the relativistic Lense--Thirring precession of the inner accretion flow, in which a hot inner flow, tilted with respect to the black hole spin axis, precesses as a solid body while a cooler outer disc remains at its own, different tilt -- a warped, Bardeen--Petterson-type geometry. Testing this picture requires a radiative-transfer model that self-consistently follows photons through such a system: from emission near the innermost stable circular orbit (ISCO), through Compton scattering in a hot corona, to possible reflection off the misaligned outer disc, all under the full effects of light bending in Kerr spacetime. In this first paper of a two-part series, we present a general-relativistic Monte Carlo (GRMC) radiative-transfer model of a misaligned, warped, two-zone accretion system around a Kerr black hole. We describe the disc--corona geometry, the seed-photon prescription, the photon-transport engine -- including the geodesic integration scheme, the coronal Compton-scattering module and the outer-disc reflection treatment -- and the observer pipeline used to construct energy spectra, photon path-length and arrival-time distributions. We present the resulting energy spectra, light curves and spectral lags as functions of the black hole mass, corona size, outer-disc geometry, reflection albedo, photon-injection radius and observer inclination, and show how gravitational light bending systematically lengthens the path-length and arrival-time distributions of the escaping radiation. This model and its spectral-timing predictions form the foundation for Paper II, which extends the framework to track the full photon polarization state and presents the resulting energy- and precession-phase-resolved polarimetric signatures.
ER -