Rotational modulation in A and F stars: magnetic stellar spots or convective core rotation?

ABSTRACT The Kepler mission revealed a plethora of stellar variability in the light curves many stars, some associated with magnetic activity or oscillations. In this work, we analyse periodic signal 162 intermediate-mass interpreted as Rossby modes and rotational modulation – so-called hump spike feature. We investigate whether (spike) is due to spots caused by fields Overstable Convective (OsC) resonantly exciting g modes, frequencies corresponding convective core rotation rate. Assuming that spikes are created at surface, recover amplitudes fields, which good agreement theoretical predictions. Our data show clear anticorrelation between mass possibly correlation age, consistent dynamo-generated theory (sub)-surface layers. Investigating harmonic behaviour, find for 125 stars neither two possible explanations can be excluded. While our results suggest field scenario more likely explain feature, assess further work needed distinguish scenarios. One method ruling out one directly observe stars. Another would impose additional constraints through detailed modelling regarding requirement OsC mode presence convective-core (stellar age).