FUNDAMENTAL PARAMETERS AND CHEMICAL COMPOSITION OF CEPHEID X SGR.

Автор(и)

  • I. A. Usenko Department of Astronomy of I.I. Mechnikov Odessa National University, T.G.Shevchenko Park, Odessa 65014 Ukraine, Ukraine
  • A. Yu. Knyazev South African Large Telescope, P.O. Box 9, Observatory, Cape Town, 7935, South Africa, South Africa
  • L. N. Berdnikov Sternberg Astronomical Institute, Moscow University, Moscow, 119899 Russia, Russian Federation
  • V. V. Kravtsov Sternberg Astronomical Institute, Moscow University, Moscow, 119899 Russia; Universidad Catolica del Norte, Avenida Angamos 0610, Autofagasta, Chile, Russian Federation

DOI:

https://doi.org/10.18524/1810-4215.2012.25.83162

Анотація

Five high-resolutioned spectra of unusual Cepheid X Sgr have been obtained during its pulsational period. For the first time we obtain accurate fundamental parameters and abundances of chemical elements, in particular of sodium, magnesium and aluminium. We estimate the mean Teff = 6143±30 K; log g = 2.00; Vt = 4.35 kms -1. The estimated effective temperature and surface gravity are relatively high compared to the typical values characteristic of Cepheids with pulsational period around 7 days. A deficit of carbon ([C/H] = -0.26±0.04 dex), overabundances of sodium ([Na/H] =+0.31±0.04 dex) and aluminium ([Al/H] = +0.21±0.08 dex) are typical for Cepheids passing through the first dredge-up phase. However, an obvious overabundance of magnesium ([Mg/H] = +0.19±0.04 dex) is unusual. The abundance of iron ([Fe/H] = -0.02±0.01 dex) is very close to the solar one. Abundances of a - elements, (those of Fe-group, as well as "light " and "heavy", s- and r-process elements) are comparable to the solar values, except for several elements showing slight over- or underabundances.

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Опубліковано

2012-11-15

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