• Lemasle, B.
• François, P.
• Bono, G.
• Mottini, M.
• Romaniello, M.
• Primas, Francesca

Abstract

Aims:The recent introduction of high-resolution/large spectral-range spectrographs has provided the opportunity to investigate the chemical composition of classical Cepheids in detail. This paper focusses on new abundance determinations for iron and 6 light metals (O, Na, Mg, Al, Si, Ca) in 30 Galactic Cepheids. We also give a new estimate of the Galactic radial abundance gradient. <BR />Methods: The stellar effective temperatures were determined using the method of line depth ratios, and the surface gravity and the microturbulent velocity v<SUB>t</SUB> by imposing the ionization balance between Fe I and Fe II with the help of curves of growth. Abundances were calculated with classical LTE atmosphere models. <BR />Results: Abundances were obtained with rms accuracies of about 0.05-0.10 dex for Fe, and 0.05-0.20 dex for the other elements. Cepheids in our sample have solar-like abundances, and current measurements agree quite well with previous determinations. We computed "single zone" Galactic radial abundance gradients for the 8-12 kpc region and found a slope for iron of -0.061 dex kpc<SUP>-1</SUP>. <P />Based on observations made with the 1.52 m ESO Telescope at La Silla, Chile....

Topics

• surface
• chemical composition
• iron