Chemically Peculiar Stars in the Open Cluster Stock 2

TL;DR

This study investigates chemically peculiar A-type stars in the open cluster Stock 2, using spectroscopic data to identify anomalies and provide benchmarks for stellar evolution models involving atomic diffusion.

Contribution

It presents the first detailed spectroscopic analysis of stars in Stock 2, identifying nine candidate Am stars and providing fundamental parameters and chemical abundances.

Findings

Identified nine A stars with anomalous chemical abundances.

Derived fundamental parameters and chemical compositions for 71 cluster stars.

Found potential benchmarks for testing stellar evolution models.

Abstract

The recently re-discovered open cluster Stock 2, located roughly 375 pc away and about 400 Myr old, has the potential to be an exciting new testbed for our understanding of stellar evolution. We present results from a spectroscopic campaign to characterize stars near the cluster's main-sequence turnoff; our goal is to identify candidate chemically peculiar stars among the cluster's A stars. We obtained echelle spectra for 64 cluster members with ESPaDOnS on the 3.6-m Canada-France-Hawaii Telescope, Mauna Kea Observatory, USA, and for six stars with SOPHIE on the 1.93-m telescope at the Observatoire de Haute-Provence, France. We complemented these new observations with those of 13 high-mass cluster members from the HARPS-N archive; our overall sample is of 71 stars. We derived the fundamental parameters (Teff, log g, [M/H]) as well as vsini for our sample using the Sliced Inverse Regression (SIR) technique, and then used iSpec to derive individual abundances of 12 chemical species. With these abundance determinations, we identified nine A stars with anomalous levels of Sc, Ca, and other metallic lines. Follow-up observations of these Am candidates with a known age can transform them into benchmarks for evolutionary models that include atomic diffusion and help build a better understanding of the complex interactions between macroscopic and microscopic processes in stellar interiors.