1 research outputs found
Baade-Wesselink distances and the effect of metallicity in classical cepheids
The aim of this paper is to investigate the metallicity dependence of the
-relation in and based on a sample of 68 Galactic Cepheids with
individual Baade-Wesselink distances (some of the stars also have an HST-based
parallax) and individually determined metallicities from high-resolution
spectroscopy. Literature values of the -band, -band and radial velocity
data have been collected for a sample of 68 classical cepheids that have their
metallicity determined in the literature from high-resolution spectroscopy.
Based on a surface-brightness relation and a projection factor derived
in a previous paper, distances have been derived from a Baade-Wesselink
analysis. - and -relations in and are derived. The effect of
the adopted dependence of the projection factor on period is investigated. The
change from a constant -factor to one recently suggested in the literature
with a mild dependence on results in a less steep slope by 0.1 unit,
which is about the 1-sigma error bar in the slope itself. The observed slope in
the -relation in in the LMC agrees with both hypotheses. In the
difference between the Galactic and LMC slope is larger and would favour a mild
period dependence of the -factor. The dependence on metallicity in and
is found to be marginal, and independent of the choice of -factor on
period. This result is severely limited by the small range in metallicity
covered by the Galactic Cepheids.Comment: A&A accepte