HARPS-N Helps to Characterize Atmospheric Parameters and Chemical Abundances of Giant Stars in 33 Open Clusters

A new study from the Stellar Population Astrophysics (SPA) project at the Telescopio Nazionale Galileo (TNG) presents a homogeneous high-resolution spectroscopic analysis of 95 giant stars across 33 open clusters in the Milky Way. Observations were carried out using HARPS-N, the TNG's high-precision spectrograph, enabling the determination of accurate non-local thermodynamic equilibrium (NLTE) atmospheric parameters and elemental abundances.

This work also provides the first-ever chemical characterization for nine of the clusters included in the sample. By adopting NLTE techniques instead of the traditional LTE (local thermodynamic equilibrium) assumptions, the study achieves improved precision in both stellar parameter estimation and chemical abundance measurements.

The authors analyzed 11 chemical elements, confirming large-scale abundance trends already known across the Galactic disk. The resulting dataset represents a new benchmark for stellar populations in open clusters and will serve as a valuable reference for upcoming spectroscopic surveys such as 4MOST and WEAVE.

By expanding the number of chemically characterized open clusters, the SPA project significantly contributes to our understanding of the formation history and chemical evolution of the Milky Way.

Link to the paper

Abundance [X/Fe] ratios as a function of age. The gray diamonds represent the OCs compilation from the GALAH survey and the gray squares represent the OCs from the OCCAM project. Our results are color-coded according to [Fe/H]. Positive correlations with age are present for elements such as Mg, Si, Ti, Al, Mn, Co, Ni, and Sr, while Na, Y and Eu show a negative trend.