Cepheid Pulsations Resolved by the VLTI
P. Kervella , D. Bersier , N. Nardetto ,
D. Mourard , P. Fouqué , V. Coudé du Foresto 
 Observatoire de Paris, France;  Space Telescope Science Institute, USA;
The very high spatial resolution provided by the VLTI makes it possible to measure directly the change in angular diameter of several southern Cepheids over their pulsation cycle. When combined with radial velocity measurements, this allowed us to measure precisely their distances in a quasi-geometrical way. This is essential information to calibrate the Cepheid's Period-Luminosity law, as well as the Period-Radius and Surface Brightness-Colour relations.
 Observatoire de la Côte d'Azur, France;  Observatoire Midi-Pyrénées, France
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