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The Interstellar Lithium Isotope Ratio Toward Per OB2

Published online by Cambridge University Press:  25 May 2016

David C. Knauth
Affiliation:
The University of Texas, Department of Astronomy, Austin, Texas, USA
Steven R. Federman
Affiliation:
The University of Texas, Department of Astronomy, Austin, Texas, USA
David L. Lambert
Affiliation:
The University of Toledo, Department of Physics and Astronomy, Toledo, Ohio, USA
Philippe Crane
Affiliation:
Dartmouth University, Department of Physics and Astronomy, Hanover, New Hampshire, USA and NASA Headquarters, Washington, DC, USA

Abstract

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We are conducting a survey on the 7Li/6Li ratio in interstellar space in order to seek limits on the variation in this ratio. The analysis is based on the technique we adopted in extracting the 11B/10B ratio. This technique uses a line of comparable strength, from a species likely to occupy the same volume of the interstellar cloud, as a template for separating velocity components within the line profile. For our study of the 7Li/6Li ratio, the K I line at 4044 Å serves as the velocity template. Our initial focus is on the variation in the 7Li/6Li ratio around the star-forming region IC 348. Our high-resolution observations of the Li I lines toward o and ζ Per show remarkably different isotope ratios: 7Li/6Li = 2-4 and 11, respectively, where the Solar System ratio is 12.3 and cosmic ray spallation yields a ratio of about 2. The significance of the very low ratio toward o Per is that it is essentially the value predicted for cosmic rays through spallation reactions. The direction to o Per passes closer to IC 348, a site of massive star formation, than does the line of sight to ζ Per. Furthermore, our analysis of OH column densities (Federman, Weber, & Lambert 1996) showed that the cosmic ray flux through o Per's diffuse clouds is higher than average, presumably reflecting the nearby presence of IC 348.

Type
4. Lithium Abundances
Copyright
Copyright © Astronomical Society of the Pacific 2000 

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