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Characterizing Kepler Asteroseismic Targets

Stellar structure and evolution can be studied in great detail by asteroseismic methods, provided data of high precision are available. We determine the effective temperature (Teff), surface gravity (log g), metallicity, and the projected rotational velocity (v sin i) of 44 Kepler asteroseismic targets using our high-resolution (R > 20,000) spectroscopic observations; these parameters will then be used to compute asteroseismic models of these stars and to interpret the Kepler light curves.We use the method of cross correlation to measure the radial velocity (RV) of our targets, while atmospheric parameters are derived using the ROTFIT code and spectral synthesis method. We discover three double-lined spectroscopic binaries, HIP 94924, HIP 95115, and HIP 97321 - for the last system, we provide the orbital solution, and we report two suspected single-lined spectroscopic binaries, HIP94112 and HIP 96062. For all stars from our sample we derive RV, v sin i, Teff, log g, and metallicity, and for six stars, we perform a detailed abundance analysis. A spectral classification is done for 33 targets. Finally, we show that the early-type star HIP 94472 is rotating slowly (v sin i = 13 kms/1) and we confirm its classification to the Am spectral type which makes it an interesting and promising target for asteroseismic modeling. The comparison of the results reported in this paper with the information in the Kepler Input Catalog (KIC) shows an urgent need for verification and refinement of the atmospheric parameters listed in the KIC. That refinement is crucial for making a full use of the data delivered by Kepler and can be achieved only by a detailed ground-based study.