LS-periodogram up to 4 d⁻¹ (left) and two spectroscopic lines (right, He Iλ5875 and H_α) for five epochs from days to months to a year, for upper main sequence stars, HD 97253, HD 151804, HD 303492, HD 38771 and HD 37128. The markers in the LS-periodogram have the same meaning as in Fig. 4. If the dominant frequency does not satisfy the significance criterion we mark it with a green cross.