  The AMBRE project is a collaboration between the European Southern
Observatory (ESO) and the Observatoire de la Cote d'Azur (OCA). It has been
established to determine the stellar atmospheric parameters (effective
temperature, surface gravity, global metallicities and abundance of
alpha-elements over iron) of the archived spectra of four ESO spectrographs.
The analysis of the ESO:HARPS archived spectra is presented. The sample being
analysed (AMBRE:HARPS) covers the period from 2003 to 2010 and is comprised of
126688 scientific spectra corresponding to 17218 different stars. For the
analysis of the spectral sample, the automated pipeline developed for the
analysis of the AMBRE: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, 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. 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 chemical index [alpha/Fe] with their associated errors have
then been estimated for all the spectra of the AMBRE:HARPS archived sample.
Based on quality criteria, we accepted and delivered the parameterisation of
~71% of the total sample to ESO. These spectra correspond to ~10706 stars; each
are observed between one and several hundred times. This automatic
parameterisation of the AMBRE:HARPS spectra shows that the large majority of
these stars are cool main-sequence dwarfs with metallicities greater than -0.5
dex.
