English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

We present the time-frequency analysis results based on the Hilbert-Huangtransform (HHT) for the evolution of a 4-Hz low-frequency quasi-periodicoscillation (LFQPO) around the black hole X-ray binary XTE J1550-564. Theorigin of LFQPOs is still debated. To understand the cause of the peakbroadening, we utilized a recently developed time-frequency analysis, HHT, fortracking the evolution of the 4-Hz LFQPO from XTE J1550 564. By adaptivelydecomposing the ~4-Hz oscillatory component from the light curve and acquiringits instantaneous frequency, the Hilbert spectrum illustrates that the LFQPO iscomposed of a series of intermittent oscillations appearing occasionallybetween 3 Hz and 5 Hz. We further characterized this intermittency by computingthe confidence limits of the instantaneous amplitudes of the intermittentoscillations, and constructed both the distributions of the QPO's high and lowamplitude durations, which are the time intervals with and without significant~4-Hz oscillations, respectively. The mean high amplitude duration is 1.45 sand 90% of the oscillation segments have lifetimes below 3.1 s. The mean lowamplitude duration is 0.42 s and 90% of these segments are shorter than 0.73 s.In addition, these intermittent oscillations exhibit a correlation between theoscillation's rms amplitude and mean count rate. This correlation could beanalogous to the linear rms-flux relation found in the 4-Hz LFQPO throughFourier analysis. We conclude that the LFQPO peak in the power spectrum isbroadened owing to intermittent oscillations with varying frequencies, whichcould be explained by using the Lense-Thirring precession model.

Characterizing Intermittency of 4-Hz Quasi-periodic Oscillation in XTE J1550-564 using Hilbert-Huang Transform