A Spectral-model-independent Diagnostic of Phase-resolved Spectral Convergence in Swift J0243.6+6124
Abstract
We introduce a spectral-model-independent spectral-shape metric, δrms, to probe phase-resolved spectral evolution in the Galactic ultraluminous X-ray pulsar Swift J0243.6+6124. The δrms--luminosity relation reveals a reproducible convergence--redivergence behavior: spectra from two geometrically opposite pulse phases converge to near identity around Lt∗∼8.8×1037 erg s−1, with a mean shape difference of only ∼2%, and rediverge at higher luminosities, most prominently at higher energies. This strong phase-resolved spectral convergence coincides with a pulse-profile reversal and traces the same transition luminosities previously identified from broadband continuum evolution, including Lt∼4.5×1037 erg s−1. These results suggest a possible luminosity-driven reweighting between a broadly distributed surface-reprocessed/reflected component and an increasingly important direct accretion-column contribution, while establishing δrms as a robust, spectral-model-independent diagnostic of radiation-geometry restructuring in bright accreting X-ray pulsars.
Versions
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BibTeX
@misc{chen2026spectralmodelindependent,
title = {{A Spectral-model-independent Diagnostic of Phase-resolved Spectral Convergence in Swift J0243.6+6124}},
author = {Bo-Yan Chen and Peng-Ju Wang and Shu Zhang and Ling-Da Kong and Long Ji and Shuang-Nan Zhang and Hua Feng and Yu-Peng Chen and Ming-Yu Ge and Jing-Qiang Peng and Qing-Cang Shui and Wen-Zhong Li},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.38232},
eprint = {2610.38232},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.38232},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - A Spectral-model-independent Diagnostic of Phase-resolved Spectral Convergence in Swift J0243.6+6124
AU - Bo-Yan Chen
AU - Peng-Ju Wang
AU - Shu Zhang
AU - Ling-Da Kong
AU - Long Ji
AU - Shuang-Nan Zhang
AU - Hua Feng
AU - Yu-Peng Chen
AU - Ming-Yu Ge
AU - Jing-Qiang Peng
AU - Qing-Cang Shui
AU - Wen-Zhong Li
PY - 2026
DA - 2026/10/28
PB - arXiv
DO - 10.48550/arxiv.2610.38232
UR - https://arxiv.org/abs/2610.38232
AB - We introduce a spectral-model-independent spectral-shape metric, δ_rms, to probe phase-resolved spectral evolution in the Galactic ultraluminous X-ray pulsar Swift J0243.6+6124. The δ_rms--luminosity relation reveals a reproducible convergence--redivergence behavior: spectra from two geometrically opposite pulse phases converge to near identity around L_t^∗∼8.8×10^37 erg s^−1, with a mean shape difference of only ∼2%, and rediverge at higher luminosities, most prominently at higher energies. This strong phase-resolved spectral convergence coincides with a pulse-profile reversal and traces the same transition luminosities previously identified from broadband continuum evolution, including L_t∼4.5×10^37 erg s^−1. These results suggest a possible luminosity-driven reweighting between a broadly distributed surface-reprocessed/reflected component and an increasingly important direct accretion-column contribution, while establishing δ_rms as a robust, spectral-model-independent diagnostic of radiation-geometry restructuring in bright accreting X-ray pulsars.
ER -