Interstellar lithium and the 7Li/6Li ratio toward rho Oph.
Abstract
We have observed the 6708 A doublet of interstellar Li I at high spectral resolution and very high SNR toward Rho Oph. In order to evaluate the interstellar lithium isotopic ratio, the data have been exhaustively analyzed by using a profile fitting method. For the first time outside the solar system, the Li-6 absorption doublet is clearly revealed by the profile analysis. We derive abundances for both lithium isotopes (Li-7/H)= 3.4 x 10 exp -9, (Li-6/H)= 2.7 x 10 exp -10, yielding the isotopic ratio (Li-7/Li-6) = 12.5 for the Rho Oph diffuse cloud. This value is in strikingly good agreement with the ratio measured in the chondritic meteorites, representative of the early solar system value, but differs largely from the only previous estimation of Ferlet and Dennefeld (1984) (Li-7/Li-6) greater than 25 toward Zeta Oph. The most recent models of lithium evolution in our Galaxy cannot as yet explain this new value toward Rho Oph.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- March 1993
- Bibcode:
- 1993A&A...269..469L
- Keywords:
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- Interstellar Matter;
- Lithium Isotopes;
- Ophiuchi Clouds;
- Resonance Lines;
- Galactic Evolution;
- Metallicity;
- Astrophysics