The solar boron, stellar lithium and deuterium, interstellar deuterium, and extragalactic deuterium abundances

摘要

D, Li, Be, and B are not by formed by ordinary stellar nucleosynthesis. D is primarily formed in the big bang. Because each generation of stars replenished the ISM with material depleted in D, the D abundance decreases with time and is larger in low-metallicity regions. Because Li, Be and B are primarily formed via cosmic-ray spallation reactions, their abundances will increase with time. Some Li and B is produced in supernovae via v-spallation reactions and some Li is produced via mass loss from Li-rich AGB stars. To determine if the B abundance has increased during past 4.5 Gyr, an accurate Solar B abundance will be determined from ongoing observations of the 1.6 mu lines of B. Initial negative results yield B/H < 3.5 x 10(-10). The Balmer D-alpha line was not detected in the high-metallicity star HD 82943; the low-metallicity Pop 11 halo star HD 140283 (both with detected Li-6), or in the slowly rotating B stars i. Her and gamma Peg with D/H < 1.0 x 10(-5). Observations of Li in super-Li-rich AGB C and S stars with strong Li lines confirms that these stars have the largest Li abundance in the Galaxy (Li/H = 10(-7) and that mass loss from these stars may contribute to the ISM Li abundance. Observations of the DCN/HCN ratio in the Galaxy yield D/H < 1.4 x 10(-6) in the Galactic Center molecular clouds (10 pc from the center) and a positive D/H gradient in the Galaxy implying that there are no Galactic sources of D and D is cosmological. Extragalactic D (in DCN) is currently being searched for in two gravitational lenses against quasars at z = 0.7 and 0.9 and in the Seyfert Galaxy NGC 1068. [References: 6]