X-ray reverberation around accreting black holes

Understand

Luminous accreting stellar mass and supermassive black holes produce power-law continuum X-ray emission from a compact central corona.

• Reverberation time lags occur due to light travel time-delays between changes in the direct coronal emission and corresponding variations in its reflection from the accretion flow.
• Reverberation is detectable using light curves made in different X-ray energy bands, since the direct and reflected components have different spectral shapes.
• Larger, lower frequency, lags are also seen and are identified with propagation of fluctuations through the accretion flow and associated corona.