High-resolution Keck I spectroscopy of Galactic halo post-asymptotic giant branch stars

C.J. Mooney, W.R.J. Rolleston, Francis Keenan, Philip Dufton, Jonathan Smoker, Robert Ryans, J.H. Aller

Research output: Contribution to journalArticlepeer-review

17 Citations (Scopus)

Abstract

Absolute and differential abundance analyses have been performed from high-resolution, high signal-to-noise ratio optical (Keck I) spectra for three evolved Galactic halo stars, namely PG 1704 + 222, HD 341617 and LSIV -0401. Their derived atmospheric parameters indicate that all three objects are undergoing a post-asymptotic giant branch (post-AGB) phase of evolution. A differential abundance analysis reveals HD 341617 as having a mild carbon deficiency of 0.74 dex, possibly due to the star having evolved off the AGB before the onset of the third dredge-up. Although such carbon underabundances are typical of hot post-AGB objects, the same trend is not observed in PG 1704 + 222, where the carbon abundance is found to be consistent with those derived for nitrogen and oxygen. Hence, a dredge-up scenario need not be invoked to explain the chemical composition of PG 1704 + 222. For LSIV -0401 no iron deficiency is apparent relative to magnesium and silicon, and hence a gas- dust separation event in the AGB progenitor need not be invoked for this star.
Original languageEnglish
Pages (from-to)851-860
Number of pages10
JournalMonthly Notices of the Royal Astronomical Society
Volume337
Issue number3
DOIs
Publication statusPublished - 11 Dec 2002

ASJC Scopus subject areas

  • Space and Planetary Science

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