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Abstract

SAPP is a pipeline designed to determine accurate parameters of stars in large surveys like Gaia-ESO and Gaia. It combines various observations, including spectra, photometry, astrometry, and asteroseismic data, using Bayesian inference. Validated with benchmark stars, SAPP breaks degeneracies between parameters, yielding precise results. For effective temperature, the typical error is about 100 K, with spectroscopic models dominating uncertainty. Log(g) uncertainty depends on observables, ranging from 0.03 dex to 0.06 dex. Metallicities are recovered with a precision of 0.03 dex for PLATO targets, improved by seismic priors. SAPP also employs an iterative scheme using nu_max = f(Teff, log g) relation, yielding robust results with small differences in temperature and metallicity. It provides fundamental parameters accurate within 1%, meeting PLATO’s goals and enabling exploration of the Galactic structure, including Radial Migration and Age Metallicity Relation. SAPP is used to investigate the alpha-poor and alpha-rich populations in the Galactic disc using Gaia-ESO spectra, Gaia EDR3 astrometry, and photometry. Non-Local Thermodynamic Equilibrium models determine parameters and abundances. A cold metal-poor alpha-poor disc is found in local distributions, suggesting co-evolution of the thick and thin disc. These distributions show well-defined trends in age and kinematic space (Vφ ). SAPP’s accurate age and abundance estimations contribute to understanding Galactic characteristics such as Radial Gradient Measurements.