HOOH rotation diagram. The detected lines (only τ = 2 ↔ 4 lines) are shown as open triangles with error bars. The size of the error bars corresponds to the total uncertainty (noise and calibration). The 3σ upper limits (not included in the fit) are shown as open squares and downward arrows and originate from transitions between τ = 1,3 states. The fitted rotation temperature is noted, as is the total column density. The column density for unpopulated τ = 1,3 states is also given.