How does distance constrain the mass of the binary, please? Let us assume data like radial velocity, light curves, and astrometry. Is there any problem in the determination of the mass of the system with unknown mass? Thank you
If you have an astrometric binary (one where both components can be resolved in an image - for example Sirius AB), then knowing the distance to the binary system can tell you what the physical scale of the orbit is by mutiplying the angular size of the orbit by the distance to the binary. i.e. You can then measure what the semi-major axis is and use this in Kepler's third law (along with the measured orbital period) to get the total system mass.
Radial velocities and light curves are irrelevant to this - the masses of eclipsing binaries can be estimated from radial velocity and light curves without knowing the distance to the binary.