TY - JOUR
T1 - Non-linear variability of quasi-periodic oscillations in GX 339-4
AU - Arur, K.
AU - Maccarone, T. J.
N1 - Publisher Copyright:
© 2019 The Author(s).
PY - 2019
Y1 - 2019
N2 - We examine the non-linear 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 non-linear coupling between low frequencies that sum to the QPO frequency as well as the 'web' pattern, where in addition to the hypotenuse, non-linear coupling between the QPO frequency and the broad-band 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.
AB - We examine the non-linear 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 non-linear coupling between low frequencies that sum to the QPO frequency as well as the 'web' pattern, where in addition to the hypotenuse, non-linear coupling between the QPO frequency and the broad-band 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.
KW - X-rays: individual: GX 339-4
KW - accretion, accretion discs
KW - binaries: close
KW - methods: statistical
KW - stars: black holes
UR - http://www.scopus.com/inward/record.url?scp=85073144322&partnerID=8YFLogxK
U2 - 10.1093/mnras/stz1052
DO - 10.1093/mnras/stz1052
M3 - Article
AN - SCOPUS:85073144322
SN - 0035-8711
VL - 486
SP - 3451
EP - 3458
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 3
ER -