EDP Sciences
Free Access
Volume 488, Number 1, September II 2008
Page(s) 25 - 35
Section Astrophysical processes
DOI https://doi.org/10.1051/0004-6361:200809859
Published online 09 July 2008

A&A 488, 25-35 (2008)
DOI: 10.1051/0004-6361:200809859

Baade-Wesselink distances and the effect of metallicity in classical cepheids

M. A. T. Groenewegen1, 2

1  Koninklijke Sterrenwacht van België, Ringlaan 3, 1180 Brussels, Belgium
    e-mail: marting@oma.be
2  Instituut voor Sterrenkunde, Celestijnenlaan 200 D, 3001 Leuven, Belgium

Received 27 March 2008 / Accepted 3 June 2008

Context. The metallicity dependence of the Cepheid PL-relation is of importance in establishing the extra-galactic distance scale.
Aims. The aim of this paper is to investigate the metallicity dependence of the PL-relation in V and K 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.
Methods. Literature values of the V-band, K-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 (V-K) surface-brightness relation and a projection factor derived in a previous paper, distances have been derived from a Baade-Wesselink analysis. PL- and PLZ-relations in V and K are derived.
Results. The effect of the adopted dependence of the projection factor on period is investigated. The change from a constant p-factor to one recently suggested in the literature with a mild dependence on $\log P$ 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 PL-relation in V in the LMC agrees with both hypotheses. In K the difference between the Galactic and LMC slope is larger and would favour a mild period dependence of the p-factor. The dependence on metallicity in V and K is found to be marginal, and independent of the choice of p-factor on period. This result is severely limited by the small range in metallicity covered by the Galactic Cepheids.

Key words: stars: distances -- stars: variables: cepheids -- cosmology: distance scale -- stars: oscillations including pulsations

© ESO 2008

Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.

Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.

Initial download of the metrics may take a while.