A unified accretion–ejection paradigm for Black Hole X-ray binaries

P.O Petrucci,J Ferreira,G Henri,L Sauge,G Pelletier

doi:10.1016/j.asr.2006.02.069

Abstract

We present a unified accretion–ejection picture that explains the different spectral state of Black Hole X-ray binaries (BHXrB) from radio to X/γ-rays. In this view, the central region of BHXrB has a multi-flow configuration which consists in (1) an outer standard accretion disc, (2) an inner magnetized accretion disc driving, (3) a self-collimated electron–proton MHD jet, surrounding and (4) a relativistic electron–positron beam when adequate conditions are met. This picture provides a simple and unified explanation to the various canonical spectral states of BH X-ray binaries, by varying the transition radius r J between the inner disc driving jets and the outer standard disc. In this framework, large r J correspond to Quiescent and Hard states while small r J correspond to Thermal Dominant ones. In between these two extremes, r J can reach values that switches on the pair cascade process giving birth to a relativistic electron–positron beam. This would correspond to the bright intermediate state.

Highlights

The time and spectral behaviors of transient X-ray binaries are important challenges for the comprehension of the accretionejection phenomena
Because we mainly focus on jet diagnostics that can be related to the underlying accretion disk, we did not use the radio fluxes detected during these two periods
While the total X-ray flux is satisfactorily reproduced (Fig. 3, top-left panel), additional comments are necessary for the evolution of both the power-law fraction PLf and the spectral index Γ

Summary

Introduction

The time and spectral behaviors of transient X-ray binaries are important challenges for the comprehension of the accretionejection phenomena. During a typical outburst cycle, the mass accretion rate onto the central compact object undergoes a sudden rise, leading to an increase in X-ray luminosity by several orders of magnitude, before decaying back to its initial value. These two phases are referred to as the rising and decaying phases. There is a striking hysteresis behavior: XrB transients show two very different physical states, and the two transitions from one state to another occur at different luminosities This provides the archetypal q-shaped curve of X-ray binaries in the so-called hardness-intensity diagram, which is an evolutionary track for which no satisfactory explanation for state transitions has been provided so far (Remillard & McClintock 2006). For recent reviews and surveys, we refer, for example, to Dunn et al (2010) or Tetarenko et al (2016)

Objectives

Methods

Results

Conclusion