Nonlinear Variability of Quasi-Periodic Oscillations in GX 339-4

Abstract

We examine the nonlinear variability of quasi-periodic oscillations (QPOs) using the bicoherence, a measure of phase coupling at different Fourier frequencies. We analyse several observations of RXTE/PCA archival data of the black hole binary GX 339-4 which show QPOs. In the type C QPOs, we confirm the presence of the 'hypotenuse' pattern where there is nonlinear coupling between low frequencies that sum to the QPO frequency as well as the 'web' pattern where in addition to the hypotenuse, nonlinear coupling between the QPO frequency and the broadband noise is present. We find that type B QPOs show a previously unknown pattern. We also show that the bicoherence pattern changes gradually from 'web' to 'hypotenuse' as the source moves from a hard intermediate state to a soft intermediate state. Additionally, we reconstruct the QPO waveforms from six observations using the biphase. Finally, we present a scenario by which a moderate increase in the optical depth of the hard X-ray emission region can explain the changes in the non-linearity seen during this transition.

9 pages, 7 figures, 1 table, accepted for publication in MNRAS Main Journal

References in corpus (3)

• Geometrical constraints on the origin of timing signals from black holes
• Inclination dependence of QPO phase lags in black hole X-ray binaries
• Phase-resolved spectroscopy of low frequency quasi-periodic oscillations in GRS 1915+105

Cited by in corpus (4)

• Phase-resolved spectroscopy of a quasi-periodic oscillation in the black hole X-ray binary GRS 1915+105 with NICER and NuSTAR
• Spectro-temporal studies of rapid transition of the quasi periodic oscillations in the black hole source H1743-322
• A broadband spectral-timing study of QPOs in the bright black hole X-ray binary Swift J1727.8-1613
• Using the bispectrum to probe radio X-ray correlations in GRS 1915+105