Lines of OIV and SIV in the Goddard High-Resolution Spectrograph spectrum of RR Tel: Constraints on atomic data

The fine-structure intervals of the 2s2p²⁴P term given by Moore (1983) appear to need revision. The flux ratios of lines within multiplet UV (0.01), which have a common upper level, depend only on transition probabilities.

The observed flux ratio of lines from the ⁴P3/2' level differs from that predicted by theory, but this difference cannot be attributed to a blend with a line of SIV]. At the electron densities in the RR Tel nebula, other flux ratios give information on the relative electron excitation rates between the ²P and ⁴ fine-structure levels. Using the collision strengths calculated by Zhang, Graziani & Pradhan, the rate to the ⁴P5/2' level, relative to the rates to the other J states, appears to be underestimated by ~ 10 per cent, which is within the expected uncertainty of 20 per cent.