[Paper Review] Is the `disappearance' of low-frequency QPOs in the power spectra a general phenomenon for Disk-Jet symbiosis?

A. Nandi, D. Radhika+1 more|arXiv (Cornell University)|Aug 21, 2013

Astrophysical Phenomena and Observations2 references3 citations

TL;DR

This study investigates the disappearance of low-frequency quasi-periodic oscillations (QPOs) in X-ray power spectra during radio flares in black hole binaries, proposing that jet ejections disrupt the inner hot corona (CENBOL), halting QPOs and softening spectra. Using RXTE/PCA data across five black hole sources, it finds consistent QPO absence, reduced rms, and spectral softening during flares, supporting a magnetized two-component advective flow (TCAF) model where magnetic field ejection evacuates the CENBOL region.

ABSTRACT

One of the best possible ways to look for disk-Jet symbiosis in galactic Black Holes is to study the correlation between X-ray and radio emissions. Beyond this study, is there any alternative way to trace the symbiosis? To answer, we investigated the X-ray features of few black hole candidates based on the archival data of PCA/RXTE. We found evidences of `disappearance' of QPOs in the power density spectra and subsequent spectral softening of the energy spectra during the radio flares (i.e., `transient' Jets). We delve deep into the nature of the accretion dynamics to understand the disk-Jet symbiosis.

Motivation & Objective

• To determine if the disappearance of low-frequency QPOs during radio flares is a general phenomenon in disk-jet symbiotic black hole systems.
• To investigate whether QPO absence correlates with spectral softening and reduced power spectral density (PSD) rms during transient jet ejections.
• To explore the physical mechanism linking jet formation to the suppression of QPOs and changes in accretion flow dynamics.
• To test the magnetized-TCAF model as an explanation for the observed spectro-temporal behavior during jet ejections.
• To establish a robust observational signature of disk-jet symbiosis beyond X-ray-radio correlation.

Proposed method

• Analyzed archival RXTE/PCA and HEXTE data from five black hole candidates (XTE J1859+226, XTE J1748-288, H 1743-322, GRO J1655-40, and others) during outbursts.
• Performed timing analysis using GHATS v1.0.1 to extract power density spectra (PDS), phase lags, and energy-dependent QPO characteristics.
• Conducted spectral fitting in 3–150 keV using diskbb, powerlaw/highecut, and phabs components to model thermal and non-thermal emission.
• Tracked evolution of QPO frequency, rms, phase lags, and spectral index across radio flare events.
• Applied the magnetized-TCAF model to interpret the physical mechanism behind QPO disappearance and spectral softening.
• Correlated X-ray timing and spectral features with radio flare activity to identify transient jet ejection phases.

Experimental results

Research questions

• RQ1 Is the disappearance of low-frequency QPOs during radio flares a consistent feature across multiple black hole binaries?
• RQ2 Does the absence of QPOs coincide with spectral softening and reduced power spectral density (PSD) rms during jet ejections?
• RQ3 Can the magnetized-TCAF model explain the observed spectro-temporal evolution during transient jet activity?
• RQ4 What is the physical mechanism linking jet formation to the disruption of the inner accretion flow (CENBOL) and QPO suppression?
• RQ5 How do the re-appearance timescales of QPOs relate to the reformation timescale of the CENBOL in the accretion flow?

Key findings

• In XTE J1859+226, QPOs disappeared completely during flares F2–F5 (2–25 keV), with spectral softening and no soft/hard energy lags observed.
• For XTE J1748-288, QPOs vanished 24 hours before a 600 mJy radio flare, accompanied by a decrease in total rms and spectral softening (spectral index steepened).
• In H 1743-322, QPOs vanished 46 hours before a 12.8 mJy bm⁻¹ radio flare at 8.4 GHz, with a transition from hard to soft-intermediate state and no phase lags.
• In GRO J1655-40, QPOs were absent for ~6 days during a radio flare, followed by re-appearance of 14 Hz QPOs 48 hours before a 6 mJy peak, with soft flux dominance and no phase lags.
• Across all sources, QPO absence, reduced total rms, lack of phase lags, and spectral softening consistently coincided with radio flares, indicating a general trend.
• QPOs reappeared as type B after flares, suggesting reformation of the CENBOL structure, with timescales ranging from hours to days.