1. Introduction
2. Observations and Data Reduction
3. Searching for Companions
3.1. Principle of the Search
3.2. Defining the Search Region
3.3. Defining the Detection Criterion
3.4. Results of the Search
4. Properties of the Detected Companions
5. Discussion
5.1. A Population of Undetected Stellar Companions?
5.2. On the PIONIER Sensitivity
6. Conclusions