Astrophys. J., 586, 268-285 (2003/March-3)
An ultra-high-resolution survey of the interstellar 7Li/6Li isotope ratio in the solar neighborhood.
KNAUTH D.C., FEDERMAN S.R. and LAMBERT D.L.
Abstract (from CDS):
In an effort to probe the extent of variations in the interstellar 7Li/6Li ratio seen previously, ultra-high-resolution (R∼360,000), high signal-to-noise spectra of stars in the Perseus OB2 and Scorpius OB2 associations were obtained. These measurements confirm our earlier findings of an interstellar 7Li/6Li ratio of about 2 toward ο Per, the value predicted from models of Galactic cosmic-ray spallation reactions. Observations of other nearby stars yield limits consistent with the isotopic ratio of ∼12 seen in carbonaceous chondrite meteorites. If this ratio originally represented the gas toward ο Per, then to decrease the original isotope ratio to its current value an order of magnitude increase in the Li abundance is expected, but it is not seen. The elemental K/Li ratio is not unusual, although Li and K are formed via different nucleosynthetic pathways. Several proposals to account for the low 7Li/6Li ratio were considered, but none seems satisfactory. Analysis of the Li and K abundances from our survey highlighted two sight lines where depletion effects are prevalent. There is evidence for enhanced depletion toward X Per, since both abundances are lower by a factor of 4 when compared to other sight lines. Moreover, a smaller Li/H abundance is observed toward 20 Aql, but the K/H abundance is normal, suggesting enhanced Li depletion (relative to K) in this direction. Our results suggest that the 7Li/6Li ratio has not changed significantly during the last 4.5 billion years and that a ratio of ∼12 represents most gas in the solar neighborhood. In addition, there appears to be a constant stellar contribution of 7Li, indicating that one or two processes dominate its production in the Galaxy.
ISM: Abundances - ISM: Atoms - Galaxy: Open Clusters and Associations: Individual: Name: Perseus OB2 - Galaxy: Open Clusters and Associations: Individual: Name: Scorpius OB2 - Galaxy: Solar Neighborhood - Stars: Individual: Constellation Name: 20 Aquilae - Stars: Individual: Constellation Name: ζ Ophiuchi - Stars: Individual: Constellation Name: χ Ophiuchi - Stars: Individual: Constellation Name: ο Persei - Stars: Individual: Constellation Name: X Persei
erratum vol. 594, p. 664 (2003)
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