The BrO3- - BrAc - Ru(bpy)(3)(2+) subsystem is shown to represent the core oscillator that serves as source of the long lasting temporal and spatial periodic behaviors in the BrO3- - H2PO2- - acetone - Mn2+ -Ru(bpy)(3)(2+) - acid "double substrate-double catalyst" oscillatory batch system. The BrAc - the substrate of the core oscillator - is formed and accumulated in the reactions taking place in the six-component system. BrAc was produced in a separate experiment with bromide, acetone, acid and excess bromate and the mixtures was used for bringing about patterns in the thin solution layer after adding the Ru(bpy)(3)(2+) catalyst. The two-dimensional reaction-diffusion patterns that appear in the subsystem and its parent system are very similar in wave speed, wavelength, color and in the duration of the pattern evolution, therefore a common chemical origin is supposed to exist in their formation. The role that the BrAc may play in the mechanism of the BrO3- - reductant - acetone - catalyst type oscillators (similar to 30 variants) is also pointed out.