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The ratio of deuterium to hydrogen in interstellar space. IV - The lines of sight to Delta, Epsilon, and Iota OrionisDeuterium absorption features in spectra of Delta, Epsilon, and Iota Ori obtained with Copernicus are analyzed. The Iota Ori line-of-sight analysis, which is quite detailed because of the high-velocity H I components superposed on the deuterium features, gives a D/H ratio (which is uncertain because of a complex profile) of 0.000014. A D/H ratio of the order of 7 millionths is determined for Delta and Epsilon Ori. For the complex line profiles involved, one may regard this as a formal lower limit. Several attempts were made to increase the ratio N(D I)/N(H I) in the context of reasonable models for the line of sight, but with no success; the derived values are therefore regarded as actual values, not lower limits. Since the derived value is an average on the line of sight, the possibility cannot be ruled out that the true ratios N(D I)/N(H I) in individual nearby components differ from the mean values. The mean value for these two directions is lower by a factor of 4 than the best value for the Zeta Pup line of sight (the highest yet derived for path lengths greater than 50 pc).
Document ID
Document Type
Reprint (Version printed in journal)
External Source(s)
Laurent, C. (Centre National de la Recherche Scientifique Verrieres-Le Buisson, France)
Vidal-Madjar, A. (CNRS, Laboratoire de Physique Stellaire et Planetaire, Verrieres-le-Buisson Essonne, France)
York, D. G. (Princeton University New Observatory, Princeton, N.J., United States)
Date Acquired
August 9, 2013
Publication Date
May 1, 1979
Publication Information
Publication: Astrophysical Journal
Subject Category
Funding Number(s)
Distribution Limits