ring-like accretion structure in M87 connecting its black hole and jet

A black hole X-ray binary produces hard X-ray radiation from its corona and disk when the accreting matter heats up. During an outburst, the disk and corona co-evolves with each other. However, such an evolution is still unclear in both its geometry and dynamics. Here we report the unusual decrease of the re fl ection fraction in MAXI J1820 + 070, which is the ratio of the coronal intensity illuminating the disk to the coronal intensity reaching the observer, as the corona is observed to contrast during the decay phase. We postulate a jet-like corona model, in which the corona can be understood as a standing shock where the material fl owing through. In this dynamical scenario, the decrease of the re fl ection fraction is a signature of the corona ’ s bulk velocity. Our fi ndings suggest that as the corona is observed to get closer to the black hole, the coronal material might be out fl owing faster.