Spectral-timing studies of X-ray binaries and AGNs with Athena

I wish to review the expected capabilities of Athena for observing bright (up to Crab) X-ray sources with the onboard calorimeter XIFU, i.e. at an unprecedented high (<10 eV) energy resolution and throughput. I will then present some examples of spectral-timing studies that will allow to probe winds and accretion flows in X-ray binaries and AGN with unprecedented details.