CAOS spectroscopy of Am stars Kepler targets

TL;DR

This study uses high-resolution spectroscopy from the CAOS instrument to analyze the stellar parameters and chemical abundances of seven Am stars in the Kepler and K2 fields, addressing discrepancies between models and observations.

Contribution

It provides the first detailed spectroscopic analysis of these Am stars using CAOS, confirming their classification and deriving key stellar parameters and abundances.

Findings

HD 43509 and HD 180347 are confirmed as Am stars.

HD 52403, HD 50766, HD 58246, HD 181206, and HD 185658 are marginal Am stars.

Oxygen abundances were derived using non-LTE analysis.

Abstract

The {\it Kepler} space mission and its {\it K2} extension provide photometric time series data with unprecedented accuracy. These data challenge our current understanding of the metallic-lined A stars (Am stars) for what concerns the onset of pulsations in their atmospheres. It turns out that the predictions of current diffusion models do not agree with observations. To understand this discrepancy, it is of crucial importance to obtain ground-based spectroscopic observations of Am stars in the {\it Kepler} and {\it K2} fields in order to determine the best estimates of the stellar parameters. In this paper, we present a detailed analysis of high-resolution spectroscopic data for seven stars previously classified as Am stars. We determine the effective temperatures, surface gravities, projected rotational velocities, microturbulent velocities and chemical abundances of these stars using spectral synthesis. These spectra were obtained with {\it CAOS}, a new instrument recently installed at the observing station of the Catania Astrophysical Observatory on Mt. Etna. Three stars have already been observed during quarters Q0-Q17, namely: HD\,180347, HD\,181206, and HD\,185658, while HD\,43509 was already observed during {\it K2} C0 campaign. We confirm that HD\,43509 and HD\,180347 are Am stars, while HD 52403, HD\,50766, HD\,58246, HD\,181206 and HD\,185658 are marginal Am stars. By means of non-LTE analysis, we derived oxygen abundances from O{\sc I}$\lambda$7771--5{\AA} triplet and we also discussed the results obtained with both non-LTE and LTE approaches.