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Abundance pipeline I

Abundance pipeline I. Line crowding/blending and telluric absorption/emission makes using equivalent widths unsuitable in the H band Spectral synthesis: the spectra will be directly fitted with model calculations

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Abundance pipeline I

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  1. Abundance pipeline I • Line crowding/blending and telluric absorption/emission makes using equivalent widths unsuitable in the H band • Spectral synthesis: the spectra will be directly fitted with model calculations • A mask will isolate the useful parts of the spectrum, ignoring telluric-contaminated regions and poorly-understood parts (e.g. unidentified/misidentified features)

  2. Abundance pipeline II • An optimization code will be used to constrain the relevant parameters from the spectra • Analysis to be carried out in two steps: • Principal atmospheric parameters: surface temperature, gravity, overall metallicity ([Fe/H]), carbon and oxygen abundances (these likely require consistent calculations of model atmospheres and fluxes) • Other abundances: less abundant elements with a negligible feedback on the atmospheric structure

  3. Abundance pipeline III • Optimization algorithm to be chosen among three existing codes using a series of blind tests (selection criteria will be accuracy and speed) • SPECFIT (Nidever): genetic algorithm • EZ_Ages (Graves & Schiavon 2008): sequential grid inversion algorithm • NGS (Lee et al. 2008): biweightaverage • FERRE (Allende Prieto 2004, 2006): Nelder-Mead algorithm The results from the first test expected within two weeks

  4. Abundance pipeline IV • Regardless of the actual algorithm, analysis based on 1D plane-parallel (Kurucz) and spherical (MARCS) model atmospheres • Fluxes consistently computed with the same background opacities used for the atmospheric structures (but more detailed line opacities) • Line opacities refined by three paths: literature compilation, laboratory work and theoretical calculations (rare earths), and empirical matching of Arcturus/solar spectra

  5. Input spectra RV from rv pipeline Abundance pipelineChart flow Coarse characterization Determ. [Si/Fe] Determ. [Si/Fe] Data pre-processing (radial velocity correction resample, filter, mask…) Data-base output Determ. [Si/Fe] Determination of Principal parameters (Teff, logg, [Fe/H], [C/Fe],[O/Fe] … Determ. [Si/Fe]

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