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Fig. 17

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HCN production rates (upper panel) and line velocity offsets (lower panel) as a function of time in comet C/2001 Q4 (NEAT) derived from the AOSA (blue circles), AOSB (red squares), and CTSB (black triangles) spectrometers which include 1-σ uncertainties. The unit of time in the horizontal axis is UT decimal days in May 2004. The time resolution is roughly 6 min with a small overhead from the telescope movement (integration of 3 min at the on-source and off-source positions in the position-switching observing mode with a relative azimuth offset of 05 between both positions using 15 s samples). Filled symbols indicate spectra that were obtained with a system temperature that was more than 1-σ away from the mean system temperature during the adjacent scans. In the upper panel, the solid line shows the best fit to the H2O apparent outgassing rates with a period of 0.8139 days obtained by fitting a sine function with one harmonic (Biver et al. 2009) scaled by the mean QHCN/QH2O during our observations. The dashed lines show linear fits to the data from the three spectrometers using a weighted linear least-squares method.

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