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Detailed chemical composition of Galactic Cepheids. A determination of the Galactic abundance gradient in the 8-12 kpc region

B. Lemasle·P. Francois·G. Bono·M. Mottini·F. Primas·M. Romaniello
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Abstract

The recent introduction of high resolution/large spectral range spectrographs provided the opportunity to investigate in detail the chemical composition of classical Cepheids. This paper is focussed 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. The stellar effective temperatures have been determined using the method of line depth ratios, while the surface gravity and the microturbulent velocity v$_{t}$ by imposing the ionization balance between Fe I and Fe II and the help of the curves of growth. Abundances were calculated with classical LTE atmosphere models. Abundances are obtained with RMS accuracies of the order of 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$^{-1}$.

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B. Lemasle, P. Francois, G. Bono, M. Mottini, F. Primas, M. Romaniello. 2007-02-13. Detailed chemical composition of Galactic Cepheids. A determination of the Galactic abundance gradient in the 8-12 kpc region. https://doi.org/10.1051/0004-6361%3A20066375

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