Analysis of the line ratio for Fe I transitions with upper common levels (Fig. 9, continued). Upper left panels: line emission in outburst; upper right panels: quiescence data. The ratios observed are compared to the theoretical calculations for a range of temperatures and column density-velocity gradients in the lower panels. The gray area shows the region for which the line emission is >5σ (in the velocity panels), and the 1σ error in the temperature and density planes.