Spectral-Timing Evolution of a Black hole X-ray binary Swift J1727.8-1613: Linking Disk Reflection and Type-C QPO Frequency During the 2023 Outburst
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| Format: | Preprint |
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2025
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| _version_ | 1866917084006449152 |
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| author | Ghising, Manoj Subba, Nirpat Tobrej, Mohammed Rai, Binay Paul, Bikash Chandra |
| author_facet | Ghising, Manoj Subba, Nirpat Tobrej, Mohammed Rai, Binay Paul, Bikash Chandra |
| contents | We present a comprehensive spectral-timing analysis of a BHXB Swift J1727.8$-$1613 during its 2023 outburst, using five pointed \textit{NuSTAR} observations sampling the luminous hard-intermediate state. Broadband 3-79 keV spectroscopy employs a physically motivated model combining a cool truncated disk (\texttt{diskbb}), relativistic reflection (\texttt{relxill} in reflection-only mode), and Comptonized continuum (\texttt{nthComp}) to probe the inner accretion geometry around a rapidly spinning black hole ($a_\ast\!=\!0.98$) at moderate inclination. Simultaneous timing analysis reveals type-C quasi-periodic oscillations (QPOs) with novel coherence evolution: the quality factor ($Q$) exhibits a striking non-monotonic dependence on both QPO frequency and luminosity, peaking near $ν_{\rm QPO}\!\sim\!1.2$~Hz and declining at both lower and higher frequencies. This turnover directly constrains Lense-Thirring precession geometry, implying optimal coherence at intermediate truncation radius. A tight photon-index-QPO-frequency correlation demonstrates that spectral softening and frequency rise are concurrent signatures of inward truncation-radius motion. The triadic luminosity evolution-rising disk and Compton, declining reflection-traces precession-driven geometry changes and corona beaming effects. Interpreting disk-normalization variability as apparent-area changes rather than physical radius swings provides new insight into disk-corona boundary layers. These quantitative results provide strong evidence for global Lense-Thirring precession regulation of both timing and spectral properties, establishing Swift J1727.8$-$1613 as a benchmark source for understanding accretion-geometry physics during black hole state transitions. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2511_12466 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Spectral-Timing Evolution of a Black hole X-ray binary Swift J1727.8-1613: Linking Disk Reflection and Type-C QPO Frequency During the 2023 Outburst Ghising, Manoj Subba, Nirpat Tobrej, Mohammed Rai, Binay Paul, Bikash Chandra High Energy Astrophysical Phenomena We present a comprehensive spectral-timing analysis of a BHXB Swift J1727.8$-$1613 during its 2023 outburst, using five pointed \textit{NuSTAR} observations sampling the luminous hard-intermediate state. Broadband 3-79 keV spectroscopy employs a physically motivated model combining a cool truncated disk (\texttt{diskbb}), relativistic reflection (\texttt{relxill} in reflection-only mode), and Comptonized continuum (\texttt{nthComp}) to probe the inner accretion geometry around a rapidly spinning black hole ($a_\ast\!=\!0.98$) at moderate inclination. Simultaneous timing analysis reveals type-C quasi-periodic oscillations (QPOs) with novel coherence evolution: the quality factor ($Q$) exhibits a striking non-monotonic dependence on both QPO frequency and luminosity, peaking near $ν_{\rm QPO}\!\sim\!1.2$~Hz and declining at both lower and higher frequencies. This turnover directly constrains Lense-Thirring precession geometry, implying optimal coherence at intermediate truncation radius. A tight photon-index-QPO-frequency correlation demonstrates that spectral softening and frequency rise are concurrent signatures of inward truncation-radius motion. The triadic luminosity evolution-rising disk and Compton, declining reflection-traces precession-driven geometry changes and corona beaming effects. Interpreting disk-normalization variability as apparent-area changes rather than physical radius swings provides new insight into disk-corona boundary layers. These quantitative results provide strong evidence for global Lense-Thirring precession regulation of both timing and spectral properties, establishing Swift J1727.8$-$1613 as a benchmark source for understanding accretion-geometry physics during black hole state transitions. |
| title | Spectral-Timing Evolution of a Black hole X-ray binary Swift J1727.8-1613: Linking Disk Reflection and Type-C QPO Frequency During the 2023 Outburst |
| topic | High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2511.12466 |