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The Exozodi survey aims to determine the occurrence rate of brightexozodiacal discs around nearby main sequence stars using infraredinterferometry. Although the Exozodi survey targets have been carefullyselected to avoid the presence of binary stars, the results of this survey canstill be biased by the presence of unidentified stellar companions. Using thePIONIER data set collected within the Exozodi survey, we aim to search for thesignature of point-like companions around the Exozodi target stars. We use boththe closure phases and squared visibilities collected by PIONIER to search forcompanions within the ~100 mas interferometric field of view. The presence of acompanion is assessed by computing the goodness of fit to the data for a seriesof binary models with various separations and contrasts. Five stellarcompanions are resolved for the first time around five A-type stars: HD 4150,HD 16555, HD 29388, HD 202730, and HD 224392 (although the companion to HD16555 was independently resolved by speckle interferometry while we werecarrying out the survey). In the most likely case of main sequence companions,their spectral types range from A5V to K4V. Three of these stars were alreadysuspected to be binaries from Hipparcos astrometric measurements, although noinformation was available on the companions themselves so far. In addition todebiasing the statistics of the Exozodi survey, these results can also be usedto revise the fraction of visual binaries among A-type stars, suggesting thatan extra ~13% A-type stars are visual binaries in addition to the ones detectedin previous direct imaging surveys. We estimate that about half the populationof nearby A-type stars could be resolved as visual binaries using a combinationof state-of-the-art interferometry and single-aperture imaging, and we suggestthat a significant fraction of these binaries remains undetected to date.

Searching for faint companions with VLTI/PIONIER. II. 92 main sequence stars from the Exozodi survey