Histograms of β₂₁. In the top panel, the blue and orange histograms are samples of wide ((R₁ + R₂)/a < 0.3) and close ((R₁ + R₂)/a ≥ 0.3) sources, respectively. In the bottom panel, the orange, green, and red histograms are samples of hot (T_eff > 5000 K), cool (T_eff ≤ 5000 K), and fast-rotating (P_rot < 3 days) sources, respectively. The vertical solid and dashed lines label β₂₁ of −2 and −2/3, respectively.