Time domain astronomy with future X-ray satellites

Accreting black holes emit in X-rays at the wave-band in which THESEUS will be observing (0.3 keV-20 MeV) due to their extreme physical conditions. The softer energy range is devoted to thermal emission from the accretion disc and the harder is due to the existence of a hard X-ray emitting corona (with undefined geometry so far). The importance of one component versus the other gives rise to the diverse state classification of accreting black holes. This accretion state can be guessed through the X-ray spectral and timing properties that will be routinely measured by THESEUS. There is also the global contribution of the X-ray fluorescence of the accretion disc by the irradiating photons from the corona, which is a powerful tool to unveil its geometry. This component gives rise to the relativistically broadened Fe lines observed in the 0.3-10 keV X-ray spectra and the time-lags of the soft 0.3-1keV energy emission with respect to the main coronal (1-4 keV) emission. The latter require huge detector areas as those present in the current and future XMM-Newton and ATHENA satellites. Nevertheless the former could be achievable (after merging pointing exposures) for the brightest sources (usually located at kpc distances). I will discuss the results obtained with realistic simulations of these features with THESEUS.