High-resolution spectra of the 6300-Å region of Comet P/Halley

Abstract

A series of high resolution spectra of the 6300-Å region of Comet P/Halley were taken with the echelle/reticon system on the 61-in. telescope at the Harvard-Smithsonian Oak Ridge Observatory from 23 October 1985 through 5 January 1986. Relative contributions of various rotational lines within the (0,8,0) band of NH 2 and of the cometary and airglow contributions of O( 1D) were clearly spectrally separated. Measurements were taken both centered on the nucleus as well as offset by various displacements in different directions. A number of important implications have resulted from the analysis of these data. (1) The relative fluxes of different rotational members of the NH 2 (0,8,0) band vary not only from day-to-day, as previously reported, but also with radial distance within the coma. Indications are that the vib-rotational structure of the band could be useful as a diagnostic for coma temperatures and/or outflow kinematics. (2) Deviations from circular symmetry were negligible for NH 2 but detectable for O( 1D), having only a small (0–10%) average sunward asymmetry. (3) The inner radial brightness distribution for O( 1D) is consistent with its production from the photodissociation of its parent (H 2O). (4) The inner radial brightness distributions for NH 2 were reasonably consistent with previously published results found for Halley and other comets. (5) Some inconsistencies were found in the comparison of the cometary NH 2 line wavelengths with the standard laboratory values.