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Advanced Abundance Pipeline for Spectral Analysis in Astronomy

This pipeline uses sophisticated techniques to analyze spectra in astronomy, focusing on abundance determination and spectral synthesis. It employs model calculations, optimization codes, and an algorithm selection process, leading to precise elemental abundance measurements. The analysis includes isolating useful spectral parts, constraining relevant parameters, and selecting the best optimization algorithm. Results are expected within two weeks of the first test. The pipeline ensures consistency with model atmospheres, accurate flux computations, and refined line opacities for detailed analysis.

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Advanced Abundance Pipeline for Spectral Analysis in Astronomy

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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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