Presentation #406.06 in the session “Stellar/Compact II (Oral)”.
Accreting black holes commonly exhibit hard X-ray emission, originating from a compact region of hot plasma commonly referred to as the corona. What powers the corona is unknown, but some models suggest the corona is related to the base of a relativistic jet. In this talk, I will disucss this jet model in the context of X-ray variability. In particular, in recent years a new tool for probing the geometry of the corona has been developed, called X-ray reverberation mapping. Some of the coronal photons irradiate the accretion flow and are reprocessed; due to differences in light travel time, the reprocessed photons lag behind those reaching us directly from the corona. While reverberation lags are now commonly detected in X-ray binaries, our models remain overly simplistic, modeling the X-ray corona as a simple point source of light. I will discuss recent efforts to move beyond this simple paradigm, with the goal of accounting for the full spatial extent of the corona. In particular, I will highlight the impact that the fully self consistent inclusion of a second lamppost, mimicking a vertically extended corona similar to the base of a jet. I will also discuss an application of this new model to new NICER observations of black hole outbursts, and discuss implications on the inferred properties of the accretion flow, black hole mass and spin.