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[28.03] On the N₂⁺/CO⁺ Ratio in Comet C/1995O1 (Hale-Bopp)

S. Wyckoff, R. S. Heyd (Arizona State University)

The nitrogen abundance in comets is critical for understanding conditions in the early solar nebula. Most models predict a relatively high nitrogen abundance in the outer solar nebula and in comets, with most of the volatile nitrogen in the form of N₂. The N₂⁺ B-X 0-0 band at 3914 A was identified in comet spectra nearly a century ago, but its identification in recent bright comets has proven difficult. Here we report a feature at 3914 A that we identify with the N₂⁺ B-X 0-0 band in a tail spectrum (resolution 2500) of comet Hale-Bopp on April 13, 1997. If this band is N₂⁺, then we find an N₂⁺/CO⁺ ratio of the same order as values found in comets 1P/1982 U1 (Halley) and C/1987 P1 (Bradfield). If the dynamics of N₂⁺ and CO⁺ were comparable in comet Hale-Bopp then the volatile N₂/CO ratio inferred in comet Hale-Bopp is much smaller than most model predictions.

The author(s) of this abstract have provided an email address for comments about the abstract: wyckoff@asu.edu

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Bulletin of the American Astronomical Society, 35 #4
© 2003. The American Astronomical Soceity.