Staring down the gravity well: an X-ray reverberation study of Cyg X-1

We propose to observe the bright persistent hard state of Cyg X-1 with the EPIC-pn in timing mode for 4 consecutive XMM-Newton orbits, in order to obtain the best ever measurements of energy-dependent time-lags in an accreting black hole. With these data we will measure lags at 6.4 keV with CCD-quality spectral resolution and an error of only 0.2 ms, enabling us to reverberation map the iron Kalpha line for the very first time in any compact object. We will also map the temperature profile of the disc blackbody emission and use the RGS data to obtain a complete picture of the structure of the stellar wind which ultimately feeds the black hole.