Constraint of the matter-ejection point position and β for q = 0.048. Left, middle, and right panels describe the constraints for m₁ values 1.4, 1.6, and 1.8 M_⊙. The red curve represents the orbital period derivative of 1.46 × 10⁻¹¹ s s⁻¹ for the pairs β–d/a. The black and blue horizontal lines represent the minimum and maximum luminosity of the source during the observations. The minimum and maximum value of d/a correspond to the inner Lagrangian point and the CS position with respect to the center of mass. The observed luminosities suggest that the mass transfer is highly non-conservative and that the ejected matter leaves the system close to the inner Lagrangian point.