Journal Article

HD 209621: abundances of neutron-capture elements*

Aruna Goswami and Wako Aoki

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 404, issue 1, pages 253-264
Published in print May 2010 | ISSN: 0035-8711
Published online April 2010 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2010.16265.x
HD 209621: abundances of neutron-capture elements*

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High-resolution spectra obtained from the Subaru Telescope High Dispersion Spectrograph have been used to update the stellar atmospheric parameters and metallicity of the star HD 209621. We have derived a metallicity of [Fe/H]=−1.93 for this star, and have found a large enhancement of carbon and of heavy elements, with respect to iron. Updates on the elemental abundances of four s-process elements (Y, Ce, Pr, Nd) along with the first estimates of abundances for a number of other heavy elements (Sr, Zr, Ba, La, Sm, Eu, Er, Pb) are reported. The stellar atmospheric parameters, the effective temperature, Teff, and the surface gravity, log g (4500 K, 2.0), are determined from local thermodynamic equilibrium analysis using model atmospheres. Estimated [Ba/Eu]=+0.35, places the star in the group of CEMP-(r+s) stars; however, the s-elements abundance pattern seen in HD 209621 is characteristic of CH stars; notably, the second-peak s-process elements are more enhanced than the first-peak s-process elements. HD 209621 is also found to show a large enhancement of the third-peak s-process element lead (Pb) with [Pb/Fe]=+1.88. The relative contributions of the two neutron-capture processes, r and s, to the observed abundances are examined using a parametric model-based analysis, which hints that the neutron-capture elements in HD 209621 primarily originate in s-process.

Keywords: stars: abundances; stars: carbon; stars: late type; stars: Population II

Journal Article.  9032 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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