Model to combined Band 5 and 6 data of HN¹³CO for B1-c in red and data in black. The model uses the lower limit on the excitation temperature of HN¹³ CO. Each graph shows one line of HN¹³CO, indicated by the solid green line at the top of the box, along with its upper energy level, written in red at the top right. The lines with upper energy levels above 1000 K and/or A_ij below 10⁻⁵ are not plotted. The excitation temperature used for the figure is shown at the top left. The dashed green line shows the 3σ level. Cases where a line is seen at the 3σ level or above and is used as part of the fitting are marked with a green X at the top right corner of the box.