STOKES tables and KY codes
Abstract
The family of KY codes is an XSPEC-compatible package of fully relativistic models for spectro-polarimetric modeling of X-ray binary systems and active galactic nuclei. Within Kerr space-time, they compute accretion disc line profiles, reflection spectra from discs illuminated by Comptonized coronal radiation, and thermal disc emission including disc-corona interaction and disc self-irradiation. Many of these models include polarimetric computations, and more advanced timing variants compute X-ray, UV and optical reverberation. The primary source of Comptonized X-rays is assumed to be in the lamp-post on-axis or slab above the disc geometry. The KY codes operate at various levels of complexity; some models use analytical approximations for local re-processing, while others rely on detailed numerical tables. For the most accurate treatment of rest-frame re-processing in partially ionized accretion disc atmospheres, the KY codes employ pre-computed spectro-polarimetric tables generated with the STOKES code. These transmission and reflection tables are also designed for standalone use in XSPEC and as inputs to higher-level models beyond KY. The chapter first introduces the STOKES tables in various variants and shows their non-relativistic usage in XSPEC models for (i) an extended source illuminating a distant geometrically thin disc, and (ii) a compact source illuminating a vertically extended equatorial obscurer (e.g., a torus or thick wind). The relativistic KY ray-tracing is then described, followed by an introduction to each KY model. Examples of fits to the IXPE data of X-ray binaries and active galactic nuclei using these models are shown. Together, these models form a comprehensive and publicly available framework for spectro-polarimetric modeling and data fitting of accretion. We provide links to their online repositories.
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BibTeX
@misc{podgorny2026stokes,
title = {{STOKES tables and KY codes}},
author = {Jakub Podgorný and Michal Dovčiak},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2608.30677},
eprint = {2608.30677},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2608.30677},
}
RIS
TY - UNPB
TI - STOKES tables and KY codes
AU - Jakub Podgorný
AU - Michal Dovčiak
PY - 2026
DA - 2026/10/23
PB - arXiv
DO - 10.48550/arxiv.2608.30677
UR - https://arxiv.org/abs/2608.30677
AB - The family of KY codes is an XSPEC-compatible package of fully relativistic models for spectro-polarimetric modeling of X-ray binary systems and active galactic nuclei. Within Kerr space-time, they compute accretion disc line profiles, reflection spectra from discs illuminated by Comptonized coronal radiation, and thermal disc emission including disc-corona interaction and disc self-irradiation. Many of these models include polarimetric computations, and more advanced timing variants compute X-ray, UV and optical reverberation. The primary source of Comptonized X-rays is assumed to be in the lamp-post on-axis or slab above the disc geometry. The KY codes operate at various levels of complexity; some models use analytical approximations for local re-processing, while others rely on detailed numerical tables. For the most accurate treatment of rest-frame re-processing in partially ionized accretion disc atmospheres, the KY codes employ pre-computed spectro-polarimetric tables generated with the STOKES code. These transmission and reflection tables are also designed for standalone use in XSPEC and as inputs to higher-level models beyond KY. The chapter first introduces the STOKES tables in various variants and shows their non-relativistic usage in XSPEC models for (i) an extended source illuminating a distant geometrically thin disc, and (ii) a compact source illuminating a vertically extended equatorial obscurer (e.g., a torus or thick wind). The relativistic KY ray-tracing is then described, followed by an introduction to each KY model. Examples of fits to the IXPE data of X-ray binaries and active galactic nuclei using these models are shown. Together, these models form a comprehensive and publicly available framework for spectro-polarimetric modeling and data fitting of accretion. We provide links to their online repositories.
ER -