The AMBRE Project: Parameterisation of FGK-type stars from the ESO:HARPS archived spectra

Context. The AMBRE project is a collaboration between the European Southern Observatory (ESO) and the Observatoire de la Côte d’Azur (OCA). It has been established to determine the stellar atmospheric parameters of the archived spectra of four ESO spectrographs. Aims. The analysis of the ESO:HARPS archived spectra for the determination of their atmospheric parameters (effective temper-ature, surface gravity, global metallicities and abundance of α-elements over iron) is presented. The sample being analysed (AM-BRE:HARPS) covers the period from 2003 to 2010 and is comprised of 126 688 scientific spectra corresponding to ∼17 218 different stars. Methods. For the analysis of the AMBRE:HARPS spectral sample, the automated pipeline developed for the analysis of the AM-BRE:FEROS archived spectra has been adapted to the characteristics of the HARPS spectra. Within the pipeline, the stellar parameters are determined by the MATISSE algorithm, which has been developed at OCA for the analysis of large samples of stellar spectra in the framework of galactic archaeology. In the present application, MATISSE uses the AMBRE grid of synthetic spectra, which covers FGKM-type stars for a range of gravities and metallicities. Results. We first determined the radial velocity and its associated error for the ∼15 % of the AMBRE:HARPS spectra, for which this velocity had not been derived by the ESO:HARPS reduction pipeline. The stellar atmospheric parameters and the associated chemica