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Oxygen Abundances in Metal-Poor Stars (-2.2 < [Fe/H] < -1.2) from Infrared OH lines

Jorge Melendez·Beatriz Barbuy·Francois Spite
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Abstract

Infrared OH lines at 1.55 - 1.56 um in the H-band were obtained with the Phoenix high-resolution spectrograph at the 2.1m telescope of the Kitt Peak National Observatory for a sample of 14 metal-poor stars. Detailed analyses of the sample stars have been carried out, deriving stellar parameters based on two methods: (a) spectroscopic parameters; (b) IRFM effective temperatures, trigonometric gravities and metallicities from Fe II lines. The Fe I lines present in the H-band region observed showed to be well fitted by the stellar parameters within $Δ$[Fe/H] < 0.15 dex. The oxygen abundances were derived from fits of spectrum synthesis calculations to the infrared OH lines. CO lines in the H- and K-bands were obtained for a subsample in order to determine their carbon abundances. Adopting the spectroscopic parameters a mean oxygen-to-iron ratio of [O/Fe] ~ +0.52 is obtained, whereas using the IRFM temperatures, Hipparcos gravities and [FeII/H], [O/Fe] ~ +0.25 is found. A mean of the two methods gives a final value of [O/Fe] ~ +0.4 for the metallicity range -2.2 < [Fe/H] < -1.2 of the sample metal-poor stars.

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Jorge Melendez, Beatriz Barbuy, Francois Spite. 2001-04-10. Oxygen Abundances in Metal-Poor Stars (-2.2 < [Fe/H] < -1.2) from Infrared OH lines. https://doi.org/10.1086/321624

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