Interferometric observations of the multiple stellar system δ Velorum

Context: The nearby (~24 pc) triple stellar system δ Velorum contains a close, eclipsing binary (Aa, Ab) discovered in 2000. Multiple systems provide an opportunity to determine the set of fundamental parameters (mass, luminosity, size, chemical composition) of coeval stars.
Aims: These parameters can be obtained with particular precision in the case of eclipsing binaries; so we exploited this potential for δ Velorum's components (Aa, Ab).
Methods: We have analysed interferometric observations of the close binary (Aa, Ab), obtained with the VINCI instrument and two VLTI siderostats. The measurements, which resolve the two components for the first time, are fitted onto the simple model of two uniformly bright, spherical stars.
Results: The observations suggest that Aa and Ab have larger diameters than expected for stars on the main sequence, hence they must be in a later evolutionary state.