Multiplicity of Galactic Cepheids from long-baseline interferometry - III. Sub-percent limits on the relative brightness of a close companion of delta Cephei
Gallenne, A.; Merand, A.; Kervella, Pierre; Monnier, J. D.; Schaefer, G. H.; Roettenbacher, R. M.; Gieren, W.; Pietrzynski, G.; McAlister, H.; ten Brummelaar, T.; Sturmann, J.; Sturmann, L.; Turner, N.; Anderson, R. I. (2016)