A unified accretion-ejection paradigm for black hole X-ray binaries

Abstract

Context. We proposed in paper I that the spectral evolution of transient X-ray binaries (XrB) is due to an interplay between two flows: a standard accretion disk (SAD) in the outer parts and a jet-emitting disk (JED) in the inner parts. We showed in papers II, III, and IV that the spectral evolution in X-ray and radio during the 2010–2011 outburst of GX 339-4 can be recovered. However, the observed variability in X-ray was never addressed in this framework. Aims. We investigate the presence of low frequency quasi-periodic oscillations (LFQPOs) during an X-ray outburst, and address the possible correlation between the frequencies of these LFQPOs and the transition radius between the two flows, rJ. Methods. We select X-ray and radio data that correspond to 3 outbursts of GX 339-4. We use the method detailed in Paper IV to obtain the best parameters rJ(t) and ṁin(t) for each outburst. We also independently search for X-ray QPOs in each selected spectra and compare the QPO frequency to the Kepler and epicyclic frequencies of the flow in rJ. Results. We successfully reproduce the correlated evolution of the X-ray spectra and the radio emission for 3 different activity cycles of GX 339-4. We use a unique normalisation factor for the radio emission, f∼R. We also report the detection of 7 new LFQPOs (3 Type B, and 4 Type C), to go along with the ones previously reported in the literature. We show that the frequency of Type C QPOs can be linked to the dynamical JED-SAD transition radius rJ, rather than to the optically thin-thick transition radius in the disk. The scaling factor q such that νQPO ≃ νK(rJ)/q is q ≃ 70 − 130, a factor consistent during the 4 cycles, and similar to previous studies. Conclusions. The JED-SAD hybrid disk configuration not only provides a successful paradigm allowing us to describe XrB cycles, but also matches the evolution of QPO frequencies. Type C QPOs provide an indirect way to probe the JED-SAD transition radius, where an undetermined process produces secular variability. The demonstrated relation between the transition radius links Type C QPOs to the transition between two different flows, effectively tying it to the inner magnetized structure, i.e., the jets. This direct connection between the jets’ (accretion-ejection) structure and the process responsible for Type C QPOs, if confirmed, could naturally explain their puzzling multi-wavelength behavior.