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

TL;DR

This study provides detailed chemical compositions of 30 Galactic Cepheids, focusing on iron and light metals, and estimates the Galactic radial abundance gradient in the 8-12 kpc region using high-resolution spectroscopy.

Contribution

It offers new abundance measurements for Cepheids and a refined estimate of the Galactic abundance gradient in the specified region.

Findings

Iron abundance gradient slope of -0.061 dex/kpc

Cepheids have solar-like elemental abundances

Abundance measurements agree with previous studies

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$^{-1}$.