arXiv subjects

S. M. Andrievsky

Publications and source records attributed to S. M. Andrievsky.

41 records · Page 3Linked to original sources

arXiv2002

Using Cepheids to determine the galactic abundance gradient. III.First results for the outer disc

As a continuation of our previous work, which concerned the radial abundance distribution in the galactic disc over the distances 4-10 kpc this paper presents the first results on the metallicicty in the outer disc (RG > 10 kpc). Based on high-resolution spectra obtained for 19 distant Cepheids we sampled galactocentric distances from 10 to 12 kpc. Combined with the results of our previous work on the inner and middle parts of the galactic disc, the present data enable one to study the structure of the radial abundance distribution over a large baseline. In particular, we find indications of a discontinuity in the radial abundance distribution for iron as well as a number of the other elements. The discontinuity is seen at a galactocentric distance RG = 10 kpc. This finding supports the results reported earlier by Twarog et al. (1997).

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arXiv2001

Using Cepheids to determine the galactic abundance gradient I. The solar neighbourhood

A number of studies of abundance gradients in the galactic disk have been performed in recent years. The results obtained are rather disparate: from no detectable gradient to a rather significant slope of about -0.1 dex kpc -1. The present study concerns the abundance gradient based on the spectroscopic analysis of a sample of classical Cepheids. These stars enable one to obtain reliable abundances of a variety of chemical elements. Additionally, they have well determined distances which allow an accurate determination of abundance distributions in the galactic disc. Using 236 high resolution spectra of 77 galactic Cepheids, the radial elemental distribution in the galactic disc between galactocentric distances in the range 6-11 kpc has been investigated. Gradients for 25 chemical elements (from carbon to gadolinium) are derived...

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arXiv2001

Using Cepheids to determine the galactic abundance gradient II. Towards the galactic center

Based on spectra obtained at the Anglo-Australian Observatory, we present a discussion of the metallicity of the galactic disc derived using Cepheids at galactocentric distances 4-6 kpc. Our new results together with previous gradient determination (Paper I) show that the overall abundance distribution within the galactocentric distances 4-11 kpc cannot by represented by a single gradient value. The distribution is more likely bimodal: it is flatter in the solar neighbourhood with a small gradient, and steepens towards the galactic center. The steepening begins at a distance of about 6.6 kpc.

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arXiv1998

Accurate LTE abundances for some lambda Boo stars

High-resolution and high S/N CCD spectra were analyzed to determine accurate LTE abundances in four lambda Boo stars: pi^1 Ori, 29 Cyg, HR 8203 and 15 And. In general, 14 chemical elements were investigated. The main results are the following: all stars have a strong deficiency of the majority of investigated metals. Oxygen exhibits a moderate deficiency. The carbon abundance is close to the solar one. The results obtained support an accretion/diffusion model, which is currently adopted for the explanation of the lambda Boo phenomenon.

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arXiv1998

The unusual A-star VW Ari: chemical composition revisited

Seven high-resolution and high S/N CCD spectra were used to derive elemental abundances in the atmosphere of VW Ari A (T_eff=7200, log g=3.7) which is the primary component of a visual binary system. The synthetic spectrum technique applied in the analysis allowed to reveal the following feature: the atmosphere of this star is strongly deficient in some metals, while light elements have solar-like abundances. Taking into account these results, one can suggest that VW Ari A is a lambda Boo-type star. Another argument supporting this supposition is the following: on the diagrams (b-y)-c_1, (b-y)-m_1 and (b-y)-beta (Paunzen et al. 1997), VW Ari A falls exactly in the region occupied by the lambda Boo stars. Note also, that a previous analysis (Andrievsky et al. 1995) has shown that the secondary component of VW Ari has a normal metallicity. Differences in chemical compositions of the two components appear to be due to the specific evolution of the primary VW Ari A.

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