A NICER view of the corona through time-dependent Comptonization of the quasi-periodic oscillations in nine black-hole X-ray binaries

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Main Authors: Zhang, Yuexin, Méndez, Mariano, Steiner, James F., García, Federico, Bellavita, Candela, König, Ole, Kara, Erin, Ramirez, Santiago Ubach, Liu, Honghui, Zhang, Zuobin, Zhang, Liang, Yang, Zi-Xu, Alabarta, Kevin, Rout, Sandeep K., Altamirano, Diego
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Published: 2026
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author Zhang, Yuexin
Méndez, Mariano
Steiner, James F.
García, Federico
Bellavita, Candela
König, Ole
Kara, Erin
Ramirez, Santiago Ubach
Liu, Honghui
Zhang, Zuobin
Zhang, Liang
Yang, Zi-Xu
Alabarta, Kevin
Rout, Sandeep K.
Altamirano, Diego
author_facet Zhang, Yuexin
Méndez, Mariano
Steiner, James F.
García, Federico
Bellavita, Candela
König, Ole
Kara, Erin
Ramirez, Santiago Ubach
Liu, Honghui
Zhang, Zuobin
Zhang, Liang
Yang, Zi-Xu
Alabarta, Kevin
Rout, Sandeep K.
Altamirano, Diego
contents We present a systematic study of the evolution of the corona geometry in nine black hole X-ray binaries (BHXRBs) using archival data from NICER. We identify 171 observations exhibiting quasi-periodic oscillations (QPOs) across various spectral states and model the time-averaged energy spectra of the source, as well as the energy-dependent rms and phase-lag spectra of the QPO, with the time-dependent Comptonization model vKompthdk. This allows us to simultaneously constrain the corona size and feedback fraction during outbursts. By using the power color hue diagnostics, we identify different spectral states, and observe that the QPO frequency increases from $\sim$0.1 Hz to $\sim$10 Hz in the low-hard and hard-intermediate states (LHS and HIMS), and remains approximately constant at 4--5~Hz in the soft-intermediate state (SIMS). The corona size shows significant evolution: the corona is large ($\sim10^4$--$10^5$ km) in the LHS, contracts rapidly to $\sim10^3$ km in the HIMS, and exhibits a flare-like expansion near the HIMS-to-SIMS transition. In the SIMS and high-soft state (HSS), the corona becomes compact and stable (4000--8000~km). The feedback fraction of the corona photons increases during the periods in which the corona contracts and decreases during the periods in which the corona expands, indicating a change of the disk-corona coupling. Our results are consistent with previous QPO-based studies using vKompthdk on some individual sources. This work, however, provides the first view of the coronal evolution across outbursts for a diverse BHXRB sample, offering critical insights into coronal behavior as a function of the spectral state of the source.
format Preprint
id arxiv_https___arxiv_org_abs_2602_07247
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle A NICER view of the corona through time-dependent Comptonization of the quasi-periodic oscillations in nine black-hole X-ray binaries
Zhang, Yuexin
Méndez, Mariano
Steiner, James F.
García, Federico
Bellavita, Candela
König, Ole
Kara, Erin
Ramirez, Santiago Ubach
Liu, Honghui
Zhang, Zuobin
Zhang, Liang
Yang, Zi-Xu
Alabarta, Kevin
Rout, Sandeep K.
Altamirano, Diego
High Energy Astrophysical Phenomena
We present a systematic study of the evolution of the corona geometry in nine black hole X-ray binaries (BHXRBs) using archival data from NICER. We identify 171 observations exhibiting quasi-periodic oscillations (QPOs) across various spectral states and model the time-averaged energy spectra of the source, as well as the energy-dependent rms and phase-lag spectra of the QPO, with the time-dependent Comptonization model vKompthdk. This allows us to simultaneously constrain the corona size and feedback fraction during outbursts. By using the power color hue diagnostics, we identify different spectral states, and observe that the QPO frequency increases from $\sim$0.1 Hz to $\sim$10 Hz in the low-hard and hard-intermediate states (LHS and HIMS), and remains approximately constant at 4--5~Hz in the soft-intermediate state (SIMS). The corona size shows significant evolution: the corona is large ($\sim10^4$--$10^5$ km) in the LHS, contracts rapidly to $\sim10^3$ km in the HIMS, and exhibits a flare-like expansion near the HIMS-to-SIMS transition. In the SIMS and high-soft state (HSS), the corona becomes compact and stable (4000--8000~km). The feedback fraction of the corona photons increases during the periods in which the corona contracts and decreases during the periods in which the corona expands, indicating a change of the disk-corona coupling. Our results are consistent with previous QPO-based studies using vKompthdk on some individual sources. This work, however, provides the first view of the coronal evolution across outbursts for a diverse BHXRB sample, offering critical insights into coronal behavior as a function of the spectral state of the source.
title A NICER view of the corona through time-dependent Comptonization of the quasi-periodic oscillations in nine black-hole X-ray binaries
topic High Energy Astrophysical Phenomena
url https://arxiv.org/abs/2602.07247