Abstract
A high dispersion spectroscopic observation of Comet 116P/Wild 4 was performed on June 10, 2003, using the High Dispersion Spectrograph (HDS) on Subaru Telescope, when the comet was at 2.4 AU from the Sun. Three forbidden oxygen emission lines in optical region, the green line at 557.7330 nm (from 1S to 1D meta-stable state) and the red doublet lines at 630.0304 and 636.3776 nm (from 1D meta-stable state to 3P state) were observed. The oxygen atoms in meta-stable state are considered to be generated by the photo-dissociation of parent molecules such as H 2O, CO, CO 2, etc. H 2O molecule is usually thought as the most dominant source of these oxygens in meta-stable state when a comet is at around 1 AU from the Sun. However, since the Comet 116P/Wild 4 was located at 2.4 AU far from the Sun at the observation, CO and/or CO 2 could be a possible main source(s) of meta-stable oxygen atoms rather than H 2O. The ratio between red doublet lines (630.0304 nm relative to 636.3776 nm) derived from our result is 2.94 ± 0.07, and the ratio of green line to the red doublet lines is 0.155 ± 0.007. The ratio of green to red doublet lines, which indicates the ratio of O( 1S) to O( 1D), give us a clue to distinguish the source of meta-stable oxygen atoms from different parent molecules. Considering the abundance of CO is comparable to or smaller than CO 2, CO 2 could be thought as the parent molecules of the meta-stable oxygen atoms as well as H 2O. The number ratio of CO 2/H 2O within our observational aperture is discussed in this paper.
Published Version
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