Abstracts > Lampens Patricia

Some 40 Kepler candidate \delta Scuti-\gamma Dor hybrid stars are currently being monitored in radial velocity in order to distinguish the true physical mechanism behind the low frequencies observed in the periodograms based on the ultra-high accuracy Kepler photometry. The physical cause for the detected low frequencies in slightly evolved or unevolved oscillating A/F-type stars (\delta Scuti stars) can be generally explained in three ways: 1) the star is an undetected binary or multiple system, 2) the star is also a g-mode pulsator (i.e. a genuine \delta Scuti-\gamma Dor hybrid), or 3) the star's atmosphere displays an asymmetric intensity distribution (due to chemical anomalies or rotational deformation) which is detected through rotational modulation. Our targets were selected from the brighter Kepler stars partly studied by Uytterhoeven et al. (2011). Our goal is to observe each star (at least) 4 times over a time period up to 2 months with the HERMES echelle spectrograph attached to the Mercator telescope. In case of multiple-lined spectra, these observations also provide the atmospheric properties of each component. As a final result, we will be able to estimate the fraction of short-period spectroscopic binary and multiple systems in the selected sample.