OXYGEN ABUNDANCES IN LOW- AND HIGH-alpha FIELD HALO STARS AND THE DISCOVERY OF TWO FIELD STARS BORN IN GLOBULAR CLUSTERS

Autor(es)

Ramirez, I. ^{[1, 2]} ; Melendez, J. ^[3] ; Chaname, J. ^[4]

Afiliação do(s) autor(es)

^[1] Univ Texas Austin, Dept Astron, Austin, TX 78712 - USA

^[2] Univ Texas Austin, McDonald Observ, Austin, TX 78712 - USA

^[3] Univ Sao Paulo, Dept Astron IAG USP, BR-05508900 Sao Paulo - Brazil

^[4] Pontificia Univ Catolica Chile, Dept Astron & Astrofis, Santiago 7820436 - Chile

• Tipo de documento: Artigo Científico
• Fonte: ASTROPHYSICAL JOURNAL; v. 757, n. 2 OCT 1 2012.
• Citações Web of Science: 54

Resumo

Oxygen abundances of 67 dwarf stars in the metallicity range -1.6 < {[}Fe/H] < -0.4 are derived from a non-LTE analysis of the 777 nm O I triplet lines. These stars have precise atmospheric parameters measured by Nissen and Schuster, who find that they separate into three groups based on their kinematics and alpha-element (Mg, Si, Ca, Ti) abundances: thick disk, high-alpha halo, and low-alpha halo. We find the oxygen abundance trends of thick-disk and high-alpha halo stars very similar. The low-alpha stars show a larger star-to-star scatter in {[}O/Fe] at a given {[}Fe/H] and have systematically lower oxygen abundances compared to the other two groups. Thus, we find the behavior of oxygen abundances in these groups of stars similar to that of the a elements. We use previously published oxygen abundance data of disk and very metal-poor halo stars to present an overall view (-2.3 < {[}Fe/H] < +0.3) of oxygen abundance trends of stars in the solar neighborhood. Two field halo dwarf stars stand out in their O and Na abundances. Both G53-41 and G150-40 have very low oxygen and very high sodium abundances, which are key signatures of the abundance anomalies observed in globular cluster (GC) stars. Therefore, they are likely field halo stars born in GCs. If true, we estimate that at least 3% +/- 2% of the local field metal-poor star population was born in GCs. (AU)

• Processo FAPESP: 10/17510-3 - Influência da formação de planetas na composição química de estrelas do tipo solar
• Beneficiário: Jorge Luis Melendez Moreno
• Modalidade de apoio: Auxílio à Pesquisa - Regular