The limb-brightened jet of M87 down to the 7 Schwarzschild radii scaleJ.-Y. Kim, T. P. Krichbaum, R.-S. Lu, E. Ros, U. Bach, M. Bremer, P. de Vicente, M. Lindqvist and J. A. ZensusA&A, 616 (2018) A188DOI: https://doi.org/10.1051/0004-6361/201832921