Accretion Flow Properties of Swift J1727.8-1613 and Estimation of the BH Mass

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Main Authors: Debnath, Dipak, Chang, Hsiang-Kuang, Nath, Sujoy Kumar, Titarchuk, Lev
Format: Preprint
Published: 2025
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author Debnath, Dipak
Chang, Hsiang-Kuang
Nath, Sujoy Kumar
Titarchuk, Lev
author_facet Debnath, Dipak
Chang, Hsiang-Kuang
Nath, Sujoy Kumar
Titarchuk, Lev
contents The rising phase of the 2023-24 outburst of the recently discovered bright transient black hole candidate Swift J1727.8-1613 was monitored by {\it Insight}-HXMT. We study the evolution of hard ($4$-150$ keV) and soft ($2$-$4$ keV) band photon count rates, the hardness ratio (HR), QPO frequencies, and spectral features using daily observations from the HXMT/LE, ME, and HE instruments between August 25 and October 5, 2023. The QPO frequency is found to be strongly correlated with the soft-band X-ray count rates, and spectral photon indices. In contrast, a strong anti-correlation is observed between HR and QPO frequency, as well as between HR and photon index. Based on the evolution of the temporal and spectral properties, the rising phase of the outburst is subdivided into six parts. The evolution of the QPOs in parts 1-5 is fitted with the propagating oscillatory shock (POS) solution to understand the nature of the evolution from a physical perspective. An inward-propagating shock with weakening strength (except in part 4) is observed during the period of our study. The probable mass of the source is estimated to be $13.5 \pm 1.9~M_\odot$ using the QPO frequency ($ν$)-photon index ($Γ$) scaling method.
format Preprint
id arxiv_https___arxiv_org_abs_2504_16391
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Accretion Flow Properties of Swift J1727.8-1613 and Estimation of the BH Mass
Debnath, Dipak
Chang, Hsiang-Kuang
Nath, Sujoy Kumar
Titarchuk, Lev
High Energy Astrophysical Phenomena
The rising phase of the 2023-24 outburst of the recently discovered bright transient black hole candidate Swift J1727.8-1613 was monitored by {\it Insight}-HXMT. We study the evolution of hard ($4$-150$ keV) and soft ($2$-$4$ keV) band photon count rates, the hardness ratio (HR), QPO frequencies, and spectral features using daily observations from the HXMT/LE, ME, and HE instruments between August 25 and October 5, 2023. The QPO frequency is found to be strongly correlated with the soft-band X-ray count rates, and spectral photon indices. In contrast, a strong anti-correlation is observed between HR and QPO frequency, as well as between HR and photon index. Based on the evolution of the temporal and spectral properties, the rising phase of the outburst is subdivided into six parts. The evolution of the QPOs in parts 1-5 is fitted with the propagating oscillatory shock (POS) solution to understand the nature of the evolution from a physical perspective. An inward-propagating shock with weakening strength (except in part 4) is observed during the period of our study. The probable mass of the source is estimated to be $13.5 \pm 1.9~M_\odot$ using the QPO frequency ($ν$)-photon index ($Γ$) scaling method.
title Accretion Flow Properties of Swift J1727.8-1613 and Estimation of the BH Mass
topic High Energy Astrophysical Phenomena
url https://arxiv.org/abs/2504.16391