Near-ultraviolet spectroscopy of Comet Austin (1989c1)

Abstract

Comet Austin (1989c1) was observed post-perihelion at a heliocentric distance near 1.25 AU. The wavelength range was from the atmospheric cutoff at 3000 to 4000 A. The coma spectra were calibrated into flux units and the contaminating sky spectrum and solar scattered light continuum were subtracted, leaving an ultraviolet spectrum of about 1.5-A resolution and excellent signal-to-noise ratio. The spectrum is dominated by emissions from OH, NH, CH, C3, and CN, some of the weaker emissions of which are seen here for the first time. More bands of CO(2+) were found than in any previous investigation and several intensity anomalies were noted; H2CO, OH(+), NCN, N(2+), and CN(+) may be present. Several emission features well above the noise level remain unidentified. The relative intensities of the OH and CN bands agree with the predictions of resonance fluorescence when one considers the potential effects of contamination by other molecules. The effects of the ozone absorption spectrum are not fully removed by the data-reduction process, although this does not affect these results.