Spectroscopic study of Kepler A-type variables

Generally, such variability in these objects is attributed to inhomogeneous surface structures (e.g. chemical spots), which are typically linked to strong magnetic fields (B>~100G) visible at the surface. It has been reported that ~44 per cent of all A-type stars observed during the Kepler mission exhibit rotationally modulated light curves.

This is surprising considering that =<10 per cent of all MS A-type stars are known to be strongly magnetic (i.e. they are Ap/Bp stars). We present a spectroscopic monitoring survey of 44 A- and late B-type stars reported to exhibit rotational modulation in their Kepler light curves. The primary goal of this survey is to test the hypothesis that the variability is rotational modulation by comparing each star's rotational broadening (vsini) with the equatorial velocities (v_eq_) inferred from the photometric periods.