Intermediate-mass Asymptotic Giant Branch Stars and Sources of ^(26)Al, ^(60)Fe, ^(107)Pd, and ^(182)Hf in the Solar System
Abstract
We explore the possibility that the short-lived radionuclides ^(26)Al, ^(60)Fe, ^(107)Pd, and ^(182)Hf inferred to be present in the proto-solar cloud originated from 3–8 M_⊙ asymptotic giant branch (AGB) stars. Models of AGB stars with initial mass above 5 M_⊙ are prolific producers of ^(26)Al owing to hot bottom burning (HBB). In contrast, ^(60)Fe, ^(107)Pd, and ^(182)Hf are produced by neutron captures: ^(107)Pd and ^(182)Hf in models ≾ 5 M_⊙, and ^(60)Fe in models with higher mass. We mix stellar yields from solar-metallicity AGB models into a cloud of solar mass and composition to investigate whether it is possible to explain the abundances of the four radioactive nuclides at the Sun's birth using one single value of the mixing ratio between the AGB yields and the initial cloud material. We find that AGB stars that experience efficient HBB (≥ 6 M_⊙) cannot provide a solution because they produce too little ^(182)Hf and ^(107)Pd relative to ^(26)Al and ^(60)Fe. Lower-mass AGB stars cannot provide a solution because they produce too little ^(26)Al relative to ^(107)Pd and ^(182)Hf. A self-consistent solution may be found for AGB stars with masses in between (4–5.5 M_⊙), provided that HBB is stronger than in our models and the ^(13)C(α, n)^(16)O neutron source is mildly activated. If stars of M < 5.5 M_⊙ are the source of the radioactive nuclides, then some basis for their existence in proto-solar clouds needs to be explored, given that the stellar lifetimes are longer than the molecular cloud lifetimes.
Additional Information
© 2017. The American Astronomical Society. Received 2016 May 11; revised 2016 December 14; accepted 2016 December 15; published 2017 February 13. This work was supported by the Epsilon Foundation (G.J.W.). One of us acknowledges the aid of Anneila Sacajawea Sargent, who guided us to Nick Scoville, who responded to the question, "Could low mass stars from earlier generations be in a molecular cloud?" M.L. is a Momentum ("Lendület-2014" Programme) project leader of the Hungarian Academy of Sciences. A.K. and M.L. warmly thank Yongzhong Qian for his help with revising the manuscript after the passing of Jerry, and thank the referee for comments that have greatly helped to improve the paper.Attached Files
Published - Wasserburg_2017_ApJ_836_126.pdf
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Additional details
- Alternative title
- Intermediate-mass Asymptotic Giant Branch Stars and Sources of 26Al, 60Fe, 107Pd, and 182Hf in the Solar System
- Eprint ID
- 74280
- Resolver ID
- CaltechAUTHORS:20170213-162656555
- Epsilon Foundation
- Hungarian Academy of Sciences
- Created
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2017-02-14Created from EPrint's datestamp field
- Updated
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2023-07-11Created from EPrint's last_modified field