The diameters ofα Centauri A and B

We compare the first direct angular diameter measurements obtained on our closest stellar neighbour, α Centauri, to recent model diameters constrained by asteroseismic observations. Using the VINCI instrument installed at ESO's VLT Interferometer (VLTI), the angular diameters of the two main components of the system, α Cen A and B, were measured with a relative precision of 0.2% and 0.6% respectively. Particular care has been taken in the calibration of these measurements, considering that VINCI is estimating the fringe visibility using a broadband K filter. We obtain uniform disk angular diameters for α Cen A and B of mas and mas, and limb darkened angular diameters of mas and mas. Combining these values with the parallax from Söderhjelm (1999), we derive linear diameters of and . These values are compatible with the masses published by Thévenin et al. (2002) for both stars.