Resolution of the [O i] + NH2 blend in comet P/Halley

Abstract

Spectra of comet P/Halley have been taken at very high resolution (0.015 nm) with a view to evaluating the contamination of the forbidden oxygen doublet at 630 nm by NH2 features at low resolution. Comparison is made with a few other bright comets. Appreciable variations are found not only in the NH2/[O I] ratio but also in the relative intensities of the various NH2 emissions themselves. The authors comment upon the accuracy obtained on the oxygen abundance derived from the [O I] lines. Mapping of these emissions over the coma is required in order to correctly remove any important NH2 contribution at low resolution. This should in addition provide information bearing upon the origin of the oxygen atoms in the 1D level.