Huss, G. R. and Fahey, A. J. and Wasserburg, G. J. (1994) Mg and Ti isotopes in presolar Al_2O_3. Meteoritics, 29 (4). pp. 475-476. ISSN 0026-1114 . http://resolver.caltech.edu/CaltechAUTHORS:20131217-115123482
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Previously, we reported O isotopic compositions and initial ^(26)Al/^(27) Al ratios for two presolar Al_2O_3 grains, Orgueil B and Bishunpur B39 [1-3]. In Orgueil B, ^(17)O/^(16)O is about twice the solar value but ^(18)O/^(16)O is normal. In B39, ^(17)O/^(16)O is ~7x higher than solar and ^(18)O/^(16)O is 0.6x the solar value. Spectroscopic observations of red giant stars show similar O compositions , which result when material that has experienced partial H burning is mixed into the stellar envelope by the first dredge-up [3,5]. The ^(17)O/^(16)O ratios indicate that Orgueil B originated around a star of ~1.5 M_☉, while B39 formed around either a ~2 Me or 4-7 M_☉ [3,5]. Both grains formed with ^(26)Al/^(27)Al ratios of ~10^(-3). Aluminum-26 is produced in the H shell after core H burning has ceased and first dredge-up has occurred. It is spread through the envelope by the third dredge-up, which occurs in low- and intermediate-mass stars as a series of mixing events driven by thermal pulses in the He shell. In intermediate-mass stars (3-8 M_☉), ^(26)Al can also be brought to the surface by the second dredge-up, which occurs at the end of core He burning.
|Additional Information:||© 1994 Meteoritical Society. Supported by NASA, NAGW-3040, NAGW-3297. Div. Contrib. No. 5409 (855).|
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|Official Citation:||Mg and Ti isotopes in presolar Al2O3 Huss, G. R.; Fahey, A. J.; Wasserburg, G. J. Meteoritics (ISSN 0026-1114), vol. 29, no. 4, p. 475-476 1994|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Ruth Sustaita|
|Deposited On:||17 Dec 2013 22:50|
|Last Modified:||17 Dec 2013 22:50|
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