Instability strip for p-mode pulsations in sdB stars. The initial points of evolutionary tracks of stars with identical core masses are connected with a grey dotted line and the masses are indicated on the plot. Envelope masses rise from left to right and range from 10^-5 M_∗ to 10^-1.8 M_∗. Sections of the tracks where more than 1 (10) p-modes with spherical degree l ≤ 3 are predicted to be excited, are coloured in green (blue). The rest of the tracks is shown in black. A sample of known p-mode pulsators are indicated with yellow points and red points indicate known hybrid pulsators.