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Please use this identifier to cite or link to this item: http://hdl.handle.net/2289/8718
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dc.contributor.authorDuraphe, Kshitij-
dc.contributor.authorMandar, Kartik-
dc.contributor.authorKhanal, Chooda-
dc.contributor.authorPareek, Abha-
dc.contributor.authorKondhiya, Tejaswi-
dc.contributor.authorSuswara, V Sree-
dc.contributor.authorDinesh, Deeksha-
dc.contributor.authorBhat, Vidyasagar-
dc.contributor.authorBhatta, Gopal-
dc.date.accessioned2026-05-25T06:27:10Z-
dc.date.available2026-05-25T06:27:10Z-
dc.date.issued2026-05-11-
dc.identifier.citationThe Astrophysical Journal, 2026, Vol. 1003(1), AR No. 13en_US
dc.identifier.issn1538-4357-
dc.identifier.urihttp://hdl.handle.net/2289/8718-
dc.descriptionOpen Access.en_US
dc.description.abstractWe present a comprehensive timing analysis of the black hole X-ray binary Cygnus X-1 using 26 NuSTAR observations spanning 2012–2024, providing the most detailed characterization to date of its accretion flow variability across spectral states. Our analysis reveals fundamental insights into the physics governing state transitions in stellar-mass black holes. We characterize the energy-dependent manifestation of the well-known bimodal state distribution, showing that raw count rate bimodality is intrinsic to the Comptonized spectral component above ∼10 keV, while thermal emission below 8 keV remains unimodal. Power spectral analysis uncovers state-dependent characteristic frequencies shifting from 0.050 Hz (hard) to 0.074 Hz (intermediate), with featureless red noise in soft states. These frequencies correspond to disk truncation radii evolving from ∼5.5 Rg to ∼2 Rg, providing direct observational evidence for the inward progression of the accretion disk during state transitions. Frequency-dependent time lags evolve systematically from ∼50 ms hard lags at 0.1 Hz in hard states to near-zero in soft states, quantifying the collapse of the Comptonizing corona. Linear root mean square–flux relations persist across all states with parameters that precisely track the relative contributions of thermal versus nonthermal emission components. Most remarkably, we identify a failed state transition (observation 30302019006) exhibiting anticorrelated band behavior, suppressed variability (Fvar < 1.38%), and apparent sub-ISCO truncation. This discovery challenges standard transition models and suggests new pathways for accretion flow evolution in wind-fed systems.en_US
dc.language.isoenen_US
dc.publisherAmerican Astronomical Societyen_US
dc.relation.urihttps://doi.org/10.3847/1538-4357/ae5632en_US
dc.rights© 2026. The Author(s)en_US
dc.subjectX-ray binary starsen_US
dc.subjectHigh mass x-ray binary starsen_US
dc.subjectHigh energy astrophysicsen_US
dc.subjectBlack hole physicsen_US
dc.subjectTiming variation methodsen_US
dc.titleState-dependent X-Ray Variability in Cygnus X-1: A 12 yr NuSTAR Timing Study of Accretion Flow Geometryen_US
dc.typeArticleen_US
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