Dwarf Cepheid Radii and the Distance Scale

Abstract

AbstractBaade-Wesselink radii for dwarf Cepheids (High Amplitude Delta Scuti stars) can give luminosities and distances independent of the classical Cepheid distance scale. Using optical and IR photometry together with precision radial velocities, the authors have obtained radii and luminosities for 7 stars, and combined these with two from the literature, obtaining results consistent with the luminosities of the 3 dwarf Cepheids with good Hipparcos parallaxes. Classical Cepheids and dwarf Cepheids appear to fit the same PL and PR relations. The results imply ‘bright’ RR Lyrae absolute magnitudes giving an LMC distance modulus of 18.51-18.54, in agreement with the distance derived from classical Cepheids.