This paper reports on the spectroscopic investigation of 238 Cepheids in the northern sky. Of these stars, about 150 are new to the study of the galactic abundance gradient. These new Cepheids bring the total number of Cepheids involved in abundance distribution studies to over 400. In this work, we also consider systematics between various studies and also those which result from the choice of models. We find that systematic variations exist at the 0.06 dex level both between studies and model atmospheres. In order to control the systematic effects our final gradients depend only on abundances derived herein. A simple linear fit to the Cepheid data from 398 stars yields a gradient d[Fe/H]/dR G = −0.062 ± 0.002 dex kpc −1 which is in good agreement with previously determined values. We have also re-examined the region of the "metallicity island" of Luck et al. With the doubling of the sample in that region and our internally consistent abundances, we find that there is scant evidence for a distinct island. We also find in our sample the first reported Cepheid (V1033 Cyg) with a pronounced Li feature. The Li abundance is consistent with the star being on its redward pass toward the first giant branch.

We present parameter and abundance data for a sample of 298 nearby giants. The spectroscopic data for this work have a resolution of R $ 60; 000, S/ N > 150, and spectral coverage from 475 to 685 nm. Overall trends in the Z > 10 abundances are dominated by Galactic chemical evolution, while the light-element abundances are influenced by stellar evolution, as well as Galactic evolution. We find several super-Li stars in our sample and confirm that Li abundances in the first giant branch are related to mixing depths. Once astration of lithium on the main sequence along with the overall range of main-sequence lithium abundances are taken into account, the lithium abundances of the giants are not dramatically at odds with the predictions of standard stellar evolution. We find the giants to be carbondiluted in accord with standard stellar evolution and that the carbon and oxygen abundances determined for the local giants are consistent with those found in local field dwarfs. We find that there is evidence for systematic carbon variations in the red giant clump in the sense that the blue side of the clump is carbon-poor (more diluted) than the red side.

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Abstract. This paper reports on the spectroscopic investigation of 12 Cepheids which are situated in the crucial region of galactocentric distances from 9 kpc to 12 kpc, where according to our previous results (Andrievsky et al. 2002c;Luck et al. 2003) the radial metallicity distribution experiences an obvious change. In particular, the wriggle in the iron abundance distribution is found to fall approximately at galactocentric distances 10-11 kpc (assuming galactocentric distance of the Sun R G, = 7.9 kpc). Within the transition zone from 10 to 11 kpc the relative-to-solar iron abundance decreases approximately to -0.2 dex. The new sample of stars, analyzed in present paper, gives results supporting the previous conclusion about the multimodal character of the metallicity distribution in galactic disc. Using a quite simple consideration of galactic chemical evolution we show that the observed distribution can be explained in the framework of a model which includes the spiral arms. In particular, the wriggle feature associated with R G ≈ 11 kpc can be interpreted as a change of metallicity level in the vicinity of the galactic corotation resonance.

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Abstract. As a continuation of our previous work on the abundance gradient in the outer part of the galactic disc, this paper presents results on the metallicicty distribution over galactocentric distances up to 15 kpc. The outer disc is clearly separated from the middle part by the existence of a step in the metallicity distribution at about 10 kpc. Taking the region of galactocentric distances from 10 kpc to 15 kpc, one can derive an iron gradient −0.03 ± 0.01 dex kpc −1 (25 stars). The existence of a discontinuity can be caused by the effective suppression of mixing processes near the corotation circle where the radial component of the gas velocity should be very small.

This paper reports on the spectroscopic investigation of 54 Cepheids, deriving parameters and abundances. These Cepheids extend previous samples by about 35% in number and increase the amount of the Galactic disk coverage, especially in the direction of l % 120 . We find that there exists in the Galactic disk at that longitude and at a solar distance of about 3Y4 kpc a region that has enhanced abundances, hFe/ H i % þ0:2, with respect to the local region. A simple linear fit to all Cepheid data now extant yields a gradient d½Fe/H /dR G ¼ À0:068 AE 0:003 dex kpc À1 . After consideration of the spatial abundance inhomogeneities in the sample, we conclude that the best current estimate of the overall gradient is d½Fe/ H /dR G ¼ À0:06 dex kpc À1 .

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