Contour lines of fixed S/N ρ as a function of the component masses m_1, 2 for BWD observed by B-DECIGO (left panel) at d = 50 Mpc and DECIGO (right panel) at d = 100 Mpc. The S/N was computed by averaging over the source orientations. The shaded gray region identifies the region where the coalescence of the two stars may lead to supernovae Ia events (Postnov & Yungelson 2014). We also show lines of constant mass ratio q = m₁/m₂.