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Cool Star Oxygen Abundances from Spectral Synthesis of TiO Bands
We have used spectral synthesis of the γ 0-0 TiO band at 7054Å to determine oxygen abundances in dwarfs previously analyzed foriron and titanium abundances from their atomic lines. With theabundances of Fe and Ti held fixed, the band profiles are sensitive tothe oxygen abundances. For the late K and M dwarfs analyzed, the [O/Fe]trend agrees with previous work for higher mass stars from to . Beyond, the TiO band becomes too weak to analyze except in cooler stars forwhich Ti abundances are difficult to determine because their Ti I linesare frequently blended. We find that the abundance trend derived for ourstars matches those derived for solar neighborhood stars by othermethods.
| Calibrating M Dwarf Metallicities Using Molecular Indices
We report progress in the calibration of a method to determine cooldwarf star metallicities using molecular band strength indices. Themolecular band index to metallicity relation can be calibrated usingchemical abundances calculated from atomic-line equivalent widthmeasurements in high-resolution spectra. Building on previous work, wehave measured Fe and Ti abundances in 32 additional M and K dwarf starsto extend the range of temperature and metallicity covered. A test ofour analysis method using warm star-cool star binaries shows we cancalculate reliable abundances for stars warmer than 3500 K. We have usedabundance measurements for warmer binary or cluster companions toestimate abundances in six additional cool dwarfs. Adding stars measuredin our previous work and others from the literature provides 76 starswith Fe abundance and CaH2 and TiO5 index measurements. The CaH2molecular index is directly correlated with temperature. TiO5 depends ontemperature and metallicity. Metallicity can be estimated to within+/-0.3 dex within the bounds of our calibration, which extends fromroughly [Fe/H]=+0.05 to -1.0, with a limited extension to -1.5.
| Micrometer measures of 401 double stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972AJ.....77..878W&db_key=AST
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