CAOS spectroscopy of Am stars Kepler targets

The Kepler space mission and its K2 extension provide photometric time series data withunprecedented accuracy. These data challenge our current understanding of the metalliclinedA stars (Am stars) for what concerns the onset of pulsations in their atmospheres. Itturns out that the predictions of current diffusion models do not agree with observations. Tounderstand this discrepancy, it is of crucial importance to obtain ground-based spectroscopicobservations of Am stars in the Kepler and K2 fields in order to determine the best estimatesof the stellar parameters. In this paper, we present a detailed analysis of high-resolutionspectroscopic data for seven stars previously classified as Am stars.We determine the effectivetemperatures, surface gravities, projected rotational velocities, microturbulent velocities andchemical abundances of these stars using spectral synthesis. These spectra were obtained withCAOS, a newinstrument recently installed at the observing station of the CataniaAstrophysicalObservatory 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 observedduring K2 C0 campaign. We confirm that HD 43509 and HD 180347 are Am stars, while HD52403, HD 50766, HD 58246, HD 181206 and HD 185658 are marginal Am stars. By meansof non-LTE (local thermodynamic equilibrium) analysis, we derived oxygen abundances fromO I λ7771–5 Å triplet and we also discussed the results obtained with both non-LTE and LTEapproaches.