Stellar Population Astrophysics (SPA) with TNG. The old open clusters
  Collinder 350, Gulliver 51, NGC 7044, and Ruprecht 171
  In the framework of the Stellar Population Astrophysics (SPA) project, we
present new observations and spectral analysis of four sparsely studied open
clusters, namely Collinder 350, Gulliver 51, NGC 7044, and Ruprecht 171. We
exploit the HARPS-N spectrograph at the TNG telescope to acquire
high-resolution optical spectra for 15 member stars of four clusters. We derive
stellar parameters using both the EW analysis and the spectral fitting
technique. We compute elemental abundances for light, a-, iron-peak, and
n-capture elements using the EW measurement approach. We investigate the origin
of the correlation between metallicity and stellar parameters derived with the
EW method for the coolest stars of the sample (Teff < 4300 K). The correlation
is likely due to the challenging continuum setting and to a general inaccuracy
of model atmospheres used to reproduce the conditions of very cool giant stars.
We locate the properties of our clusters in the radial distributions of
metallicity and abundance ratios, comparing our results with clusters from the
Gaia-ESO and APOGEE surveys. We present the [X/Fe]-[Fe/H] and [X/Fe]-Rgc trends
for elements in common between the two surveys and derive the C and Li
abundances as a function of the evolutionary phase and compare them with
theoretical models. The SPA survey allows us to fully characterise the
chemistry of nearby clusters. With a single set of spectra, we provide chemical
abundances for some chemical elements, which are comparable to those obtained
in two of the largest surveys combined. The metallicities and abundance ratios
of our clusters fit very well in the radial distributions defined by the recent
literature, reinforcing the importance of star clusters to outline the spatial
distribution of abundances in our Galaxy. Moreover, the abundances of C and Li
agree with evolutionary prescriptions for their masses and metallicities.
