The Projection Factor of Cepheids

摘要

The projection factor used in Baade-Wesselink methods of determining the distance of Cepheids is a crucial link between stellar physics and the cosmologi-cal distance scale. A coherent picture of this physical quantity is now available from high resolution spectroscopy and hydrodynamical modelling. Recent observations of 36 LMC Cepheids bring new constrains on the projection factor and new insights on the universality of the period-luminosity relation.