The abundance pattern of the yellow symbiotic star He2-467

Claudio B. Pereira, Verne V. Smith, Katia Cunha

Research output: Contribution to journalArticlepeer-review

32 Scopus citations

Abstract

We report on the analysis of high-resolution optical spectra of the yellow component of the symbiotic star He2-467. The chemical composition of its atmosphere reveals He2-467 to be a metal-poor K giant with [Fe/H] = -1.1. From a set of 14 Fe I lines, its radial velocity is found to be -106.9 ± 0.5 km s-1. This high velocity plus low metallicity points to He2-467 being a halo star. The K giant in He2-467 is also enriched in the heavy s-process elements. Because its luminosity is below that for an asymptotic giant branch (AGB) star that could have commenced shell helium-burning (via thermal pulses) and become self-enriched in the neutron-capture elements, we ascribe its heavy-element excess to the barium star phenomenon. In this scenario, the secondary component accreted matter from the primary (now the white dwarf) when it was a thermally pulsing AGB star overabundant in s-process elements. The heavy-element abundance distribution of He2-467, as well as its atmospheric parameters, is almost identical to two yellow symbiotics analyzed previously, AG Dra and BD -21°3873. In particular, its neutron exposure parameter, τ, which characterizes the s-process abundance distribution, is larger than for solar metallicities (with a single-exposure τ = 1.1 millibarn-1). Also, analysis of the rubidium abundance in He2-467 reveals that the s-process ratio of N(Rb)/N(Zr) is much larger than for solar metallicity s-process material, indicating that the s-process neutron density is considerably larger at lower metallicities, in agreement with the 13C(α, n)16O neutron source.

Original languageEnglish (US)
Pages (from-to)1977-1983
Number of pages7
JournalAstronomical Journal
Volume116
Issue number4
DOIs
StatePublished - Oct 1998
Externally publishedYes

Keywords

  • Stars: abundances
  • Stars: chemically peculiar

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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