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The star V766 Cen (=HR 5171A) was originally classified as a yellowhypergiant but lately found to more likely be a 27-36 Msun red supergiant(RSG). Recent observations indicated a close eclipsing companion in the contactor common-envelope phase. Here, we aim at imaging observations of V766 Cen toconfirm the presence of the close companion. We used near-infrared H -bandaperture synthesis imaging at three epochs in 2014, 2016, and 2017, employingthe PIONIER instrument at the Very Large Telescope Interferometer (VLTI). Thevisibility data indicate a mean Rosseland angular diameter of 4.1+/-0.8 mas,corresponding to a radius of 1575+/-400 Rsun. The data show an extended shell(MOLsphere) of about 2.5 times the Rosseland diameter, which contributes about30% of the H-band flux. The reconstructed images at the 2014 epoch show acomplex elongated structure within the photospheric disk with a contrast ofabout 10%. The second and third epochs show qualitatively and quantitativelydifferent structures with a single very bright and narrow feature and highcontrasts of 20-30%. This feature is located toward the south-western limb ofthe photospheric stellar disk. We estimate an angular size of the feature of1.7+/-0.3 mas, corresponding to a radius of 650+/-150 Rsun, and giving a radiusratio of 0.42+0.35/-0.10} compared to the primary stellar disk. We interpretthe images at the 2016 and 2017 epochs as showing the close companion, or acommon envelope toward the companion, in front of the primary. At the 2014epoch, the close companion is behind the primary and not visible. Instead, thestructure and contrast at the 2014 epoch are typical of a single RSG harboringgiant photospheric convection cells. The companion is most likely a cool giantor supergiant star with a mass of 5+15/-3 Msun.

Multi-epoch VLTI-PIONIER imaging of the supergiant V766 Cen: Image of the close companion in front of the primary