The SAPP pipeline for the determination of stellar abundances and atmospheric parameters of stars in the core program of the PLATO mission

We introduce the SAPP (Stellar Abundances and atmospheric Parameters Pipeline)the prototype of the code that will be used to determine parameters of stars observed within the core program of the PLATO space mission. The pipeline is based on the Bayesian inference and provides effective temperaturesurface gravitymetallicitychemical abundancesand luminosity. The code in its more general version has a much wider range of potential applications. It can also provide massesagesand radii of stars and can be used with stellar types not targeted by the PLATO core programsuch as red giants. We validate the code on a set of 27 benchmark stars that includes 19 FGK-type dwarfs6 GK-type subgiantsand 2 red giants. Our results suggest that combining various observables is the optimal approachas this allows the degeneracies between different parameters to be broken and yields more accurate values of stellar parameters and more realistic uncertainties. For the PLATO core samplewe obtain a typical uncertainty of 27 (syst.) ± 37 (stat.) K for T_eff0.00 ± 0.01 dex for log g0.02 ± 0.02 dex for metallicity [Fe/H]-0.01 ± 0.03 R_⊙for radii-0.01 ± 0.05 M_⊙for stellar massesand -0.14 ± 0.63 Gyr for ages. We also show that the best results are obtained by combining the ν_maxscaling relation with stellar spectra. This resolves the notorious problem of degeneracieswhich is particularly important for F-type stars.