IUE and other new observations of the slow nova RR Tel

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Abstract
Ultraviolet spectra of RR Tel taken with the International Ultraviolet Explorer satellite are reported. These cover the range 1150–3200 Å at both high and low dispersion through both large and small apertures. A range of exposure times yields a dynamic range of 1000 in line intensities. A line list of 431 lines is presented giving measured wavelength, intensity and full width at half maximum. Over three-quarters of the lines are identified. There is a correlation of linewidth with ionization energy. Lines identified include common species from once to four times ionized. Lines seen are generally resonance, semi-forbidden or forbidden lines but some recombination lines are also found for C, O and Ne. Many Fe II lines are present – most are from odd levels near 5 eV to even low-lying levels but decays from even 10 eV levels are also seen. One-third of the decays from the 5 eV levels are part of a cascade from higher levels. Population of the 10 eV levels may be due to Lα fluorescence. Diagnosis of densities and temperatures gives densities in the range log ne = 5.2 to 6.7 and temperatures of T = 11 600 to 19 000 K. Forbidden line wavelengths are used to refine intersystem separations of energy levels in some species. Low-dispersion data yield a continuum energy distribution. The strength of the λ 2175 feature and the He II Paschen line intensities yield E(B–V) = 0.10 mag. The continuum energy distribution is not due to a simple combination of gaseous emission processes and a hot star or accretion disc but the very high ratio of the energy in the lines to that in the continuum of 2.4 argues that a high temperature source must be present. New ground-based photometry finds variations of order 0.03 mag rms from night to night and within a night. If due to the lines this, in combination with the emission measure, would interestingly constrain the distance, but alternatively the variation may be seated in the continuum.

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