Excitation analysis for Comet 13P/Olbers. (a) Line-by-line nucleus-centered CO production rates (Section 4.1). (b) Linear least-squares slope fit as a function of rotational temperature, with the best-fit (optimal) T_rot (53 ± 1 K) corresponding to a slope of zero (the horizontal red line). (c) Line-by-line H₂O production rates for T_rot (opt) = 53 K. (d) Same as panel (c), but for its formal best-fit T_rot using the 13 brightest water lines. For both CO and H₂O, line numbers correspond to those assigned (arbitrarily) in Figure 2(a). Details are given in Section 3.3.