Grids of n_e and T_e for the C⁰ line ratios of each of the five stars. Black contours are the 1, 2, and 3σ confidence intervals on the best-fitting combination of n_e and T_e for the detected emission lines, given by the black dot. Gray contours are the 1, 2, and 3σ confidence intervals on the non-detected lines at 0.985 and 1.055 μm. The non-detections preclude the high density, high temperature solutions to the detected line fits seen in, e.g., CW Tau. The bottom right panel is a representative cartoon of the slab model, with the photoexcited cap and optically thick, collisionally excited core.