Derived limit N/C > 153 (red triangle) compared with evolutionary models. WD and He-star channel models are taken from Nelemans et al. (2010). WD donor tracks with progenitor masses of 1.0, 1.5, and 2.0 M_⊙ (from top to bottom) are shown as solid lines. The possible He-star donor region is indicated by the shaded area, with two examples for initial orbital periods of 20 and 60 min (upper and lower dashed lines). The CV-channel model (dashed line) is calculated using the system parameters listed in Table 3.