Publication Date:
2019-06-27
Description:
Recent laboratory, geophysical, and theoretical determinations of the O I (7990 A) and O I (11,287 A) branching ratios indicate that the generally used values based on the NBS transition parameters need revision. The O I (7990 A) branching ratio is about 300 times smaller than the NBS value, and the O I (11,287 A) is about one-quarter as large. The transitions are important in the generation of permitted atomic oxygen spectra in several types of astronomical source, including the Orion Nebula (M42), the Seyfert galaxy NGC 4151, Arcturus, and comets. The absence of the O I (7990 A) emission in M42 and NGC 4151 is consistent with its very small branching ratio, and previous conclusions based on its absence, such as the rejection of starlight excitation in the Seyfert galaxy, require reinvestigation. The reduction of the O I (11,287 A) branching ratio is pertinent to hydrogen L-beta fluorescence excitation of O I (1304 A) and O I (8446 A) emission and requires an upward revision of oxygen production rates in comets.
Keywords:
ASTROPHYSICS
Type:
Astrophysical Journal; vol. 229
Format:
text
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