Modelling spectral and timing properties of accreting black holes: the hybrid hot flow paradigm

Understand

The general picture that emerged by the end of 1990s from a large set of optical and X-ray, spectral and timing data was that the X-rays are produced in the innermost hot part of the accretion flow, while the optical/infrared (OIR) emission is mainly produced by the irradiated outer thin accretion disc.

• Recent multiwavelength observations of Galactic black hole transients show that the situation is not so simple.
• Fast variability in the OIR band, OIR excesses above the thermal emission and a complicated interplay between the X-ray and the OIR light curves imply that the OIR emitting region is much more compact.
• One of the popular hypotheses is that the jet contributes to the OIR emission and even is responsible for the bulk of the X-rays.