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May 2, 2026The Astrophysical Journal0 citationsOpen Access

Spectrotemporal Evolution in XTE J1701-462 during Its 2022 Outburst as Revealed by NICER

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NTNeal Titus ThomasKJKhushi JirawalaSGSB Gudennavar

Key Points

  • This study aims to analyze the spectrotemporal evolution of XTE J1701−462 during its 2022 outburst.
  • Utilized 57 NICER observational epochs to analyze lightcurves and spectral properties.
  • Employed broadband spectral modeling with a Comptonized disk-blackbody model to assess spectral parameters.
  • Examined state-resolved hardness–intensity diagrams to identify accretion states.
  • Identified six distinct accretion states with notable deviations indicating changes in coronal geometry.
  • Detected a quasiperiodic oscillation at ∼27 Hz with a quality factor Q ∼ 3.4 during specified epochs.
  • Estimated peak accretion rate of ∼1.21 Edd, indicating near- or super-Eddington luminosities.

Abstract

Abstract We present a comprehensive spectrotemporal study of the 2022 outburst of the transient neutron star low-mass X-ray binary (NS-LMXBs) XTE J1701−462 using 57 NICER observational epochs (E1−E57). The 0.8−10 keV lightcurve exhibits a FRED-like profile with multiple rebrightenings and intensity dips, indicating a nonmonotonic evolution of the accretion flow. Broadband spectral modeling with an absorbed Comptonized disk-blackbody model reveals a coherent evolution of spectral parameters consistent with changes in the disk−corona geometry driven by a varying mass accretion rate. The Γ − F bol diagram shows distinct clustering, enabling the identification of six accretion states: LHS-1, IMS-1, HSS, IMS-2, LHS-2, and QS. These states trace the expected cycle of disk truncation, inward propagation, and recession, with notable deviations such as sustained coronal heating in IMS-1 and the HSS, likely caused by changes in coronal geometry or the limited bandpass of NICER. State-resolved hardness–intensity diagrams reveal that XTE J1701−462 exhibits a hybrid phenomenology: island and banana branches characteristic of atoll-state early in the outburst, followed by well-defined horizontal and normal branches during IMS-1 and the HSS. As the source decays through IMS-2 and LHS-2, the HID returns to isolated clumps with increasing hardness before entering quiescence. We detected a quasiperiodic oscillation (QPO) at ∼27 Hz with a quality factor Q ∼ 3.4 during epochs E30 and E31. A Crab-based cross-calibration between NICER and NuSTAR shows that XTE J1701−462 reached a peak accretion rate of ∼1.21 m ̇ Edd , suggesting near- or super-Eddington luminosities consistent with its 2006 outburst.

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Cite This Study

Thomas et al. (2026) studied this question.

synapsesocial.com/papers/69f5939871405d493affea50https://doi.org/10.3847/1538-4357/ae5a2e
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