Oxygen abundances in halo giants. I - Giants in the very metal-poor globular clusters M92 and M15 and the metal-poor halo field

Citations Over TimeTop 19% of 1991 papers

Abstract

Oxygen, iron, vanadium, and scandium abundances are derived for very metal-poor giants in the globular clusters M92 and M15, and giants of comparable metallicity in the local halo field. The forbidden O I line dublet (6300, 6363) and nearby metallic lines in spectra are analyzed using line analysis and spectral synthesis codes. The Fe/H abundance for M92 is estimated at -2.25 +/-0.02 based on nine giants with a range of 500 K in effective temperature. No evidence for star-to-star variations in the Fe/H abundance was found. O-rich and O-poor stars appear intermixed in the H-R diagram. O - N nuclear synthesis and mixing to the surface are proposed as the best explanation for the low-oxygen giants. The nitrogen abundances obtained earlier for nine of the ten halo field giants in this sample are incompatible with the very large nitrogen abundances expected of the O/Fe abundance of about + 1.2 in halo field subdwarfs, as found by Abia and Rebolo (1989), and not more than 0.6 in halo giants, as found in this and other studies.

Related Papers

• → Globular cluster contributions to Galactic halo assembly(2012)1 cited
• → Three Parameters for the Horizontal-Branch Morphology in Globular Clusters(2013)1 cited
• METALLICITY OF GLOBULAR CLUSTER M13 FROM VI CCD PHOTOMETRY(2000)
• Three parameters for the horizontal-branch morphology in globular clusters(2013)
• Globular Clusters and the Galactic Halo Population(1987)