Chemical composition of A and F dwarfs members of the Pleiades open cluster

TL;DR

This study analyzes the chemical abundances of A and F dwarf stars in the Pleiades cluster to test stellar evolution models, revealing element abundance patterns and star-to-star variations that inform understanding of stellar processes.

Contribution

It provides detailed abundance measurements for Pleiades A and F dwarfs and compares them with evolutionary model predictions, highlighting abundance scatter and potential hydrodynamical effects.

Findings

F stars show solar abundances for most elements.

A stars exhibit larger abundance variations and correlations with Fe.

Predicted abundance patterns are confirmed for some elements.

Abstract

Abundances of 18 chemical elements have been derived for 16 A (normal and chemically peculiar CP) and 5 F dwarfs members of the Pleiades open cluster in order to set constraints on evolutionary models. The abundances, rotational velocities and microturbulent velocities were derived by iteratively adjusting synthetic spectra to observations at high resolution (R~42000 and R~75000) and high signal-to-noise (S/N) ratios. The abundances obtained do not exhibit any clear correlation with the effective temperature nor the projected rotational velocity. Interestingly, A stars exhibit larger star-to-star variations in C, Sc, Ti, V, Cr, Mn, Sr, Y, Zr and Ba than F stars. F stars exhibit solar abundances for almost all the elements. In A stars, the abundances of Si, Ti and Cr are found to be correlated with that of Fe, the [X/Fe] ratios being solar for these three elements. The derived abundances have been compared to the predictions of published evolutionary models at the age of Pleiades (100 Myr). For the F stars, the predicted slight underabundances of light elements and overabundances of Cr, Fe and Ni are indeed confirmed by our findings. For A stars, the predicted overabundances in iron peak elements are confirmed in a few stars only. The large scatter of the abundances in A stars, already found in the Hyades, Coma Berenices and the UMa group and in field stars appears to be a characteristic property of dwarf A stars. The occurence of hydrodynamical processes competing with radiative diffusion in the radiative zones of the A dwarfs might account for the found scatter in abundances.