Left: probability density functions for the estimated β from N = 10 000 systems sampled at true β = 0.2. The black solid line corresponds to the estimation performed assuming a common value of β for primary and secondary star; the red dashed line corresponds to the β values for the primary star alone; the greed dot-dashed line to β values for the secondary star alone. Right: probability density function for the differences of the estimated β for primary and secondary stars.