(a) Orbital separation, a, vs. mass ratio, q = M₁/M₂, for a brown dwarf binary, showing the maximum separation at which the secondary mass fills its Roche lobe for primary masses of 30 M_J (thick line) and 70 M_J (thin line). The dotted boundary indicates the maximum q = 0.63 required for sustained mass loss. (b) Maximum primary radial velocities (solid lines) and orbital periods (dashed lines) for a Roche lobe–filling secondary, for primary masses of 30 M_J (thick lines) and 70 M_J (thin lines). The limit q = 0.63 is indicated as above.