2011MNRAS.411.1167C

We report spectroscopic observations for 19 δ Sct candidates observed by the Kepler satellite both in long and short cadence mode. For all these stars, by using spectral synthesis, we derive the effective temperature, the surface gravity and the projected rotational velocity. An equivalent spectral-type classification has been also performed for all stars in the sample. These determinations are fundamental for modelling the frequency spectra that will be extracted from the Kepler data for asteroseismic inference. For all the 19 stars, we also present periodograms obtained from Kepler data. We find that all stars show peaks in both low- (γ Dor; g-mode) and high-frequency (δ Sct; p-mode) regions. Using the amplitudes and considering 5 cycles/d as a boundary frequency, we classified three stars as pure γ Dor, four as γ Dor-δ hybrid Sct, five as δ Sct-γ Dor hybrid and six as pure δ Sct. The only exception is the star KIC 05296877, which we suggest could be a binary.

This work is based on spectra taken at the Loiano (INAF - OA Bologna) and Serra La Nave (INAF - OA Catania) Observatories.