Inclination dependence of the non linear variability of QPOs.
Abstract
Quasi-periodic oscillations (QPOs) are features that appear as peaks in the power spectrum of X-ray binaries. The bicoherence is a measure of phase coupling among triplets of frequencies, and can be used to break degeneracies between models that produce very similar power spectra. Here we present the results of a systematic study of the effects the orbital inclination angle has on the bicoherence of observations with a QPO. We find that the high inclination (face on) and low inclination (edge on) sources exhibit different behavior as they transition from a hard intermediate to a soft intermediate state. We also present a model that suggests that this behavior can be explained by having a moderate optical depth hard X-ray emission region, so that the opacity varies significantly with inclination angle.
- Publication:
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AAS/High Energy Astrophysics Division
- Pub Date:
- March 2019
- Bibcode:
- 2019HEAD...1711212A