Comparison of continuum light curves emitted by BBH systems when only the secondary BH is active (top two rows) and both the two BH are active (bottom two rows) for e = 0.5 and i_obs = 60°. In each row, the top panels show the profiles at six phases (0 to 5π/3) in one period, and the relative flux variations are shown in the corresponding bottom panels as that in Fig. 4. Columns from left to right show the cases with ω = 0° ,90° ,180°, and 270°, which reflects the profile variations caused by different eccentricity vectors of the elliptical orbits observed at a fixed viewing angle.