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Intermediate-mass Asymptotic Giant Branch Stars and Sources of ^(26)Al, ^(60)Fe, ^(107)Pd, and ^(182)Hf in the Solar System

Wasserburg, G. J. and Karakas, Amanda I. and Lugaro, Maria (2017) Intermediate-mass Asymptotic Giant Branch Stars and Sources of ^(26)Al, ^(60)Fe, ^(107)Pd, and ^(182)Hf in the Solar System. Astrophysical Journal, 836 (1). Art. No. 126. ISSN 0004-637X. doi:10.3847/1538-4357/836/1/126.

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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.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Wasserburg, G. J.0000-0002-7957-8029
Karakas, Amanda I.0000-0002-3625-6951
Alternate Title:Intermediate-mass Asymptotic Giant Branch Stars and Sources of 26Al, 60Fe, 107Pd, and 182Hf in the Solar System
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.
Group:Lunatic Asylum
Funding AgencyGrant Number
Epsilon FoundationUNSPECIFIED
Hungarian Academy of SciencesUNSPECIFIED
Subject Keywords:nuclear reactions, nucleosynthesis, abundances; stars: AGB and post-AGB; ISM: abundances
Issue or Number:1
Record Number:CaltechAUTHORS:20170213-162656555
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Official Citation:G. J. Wasserburg et al 2017 ApJ 836 126
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:74280
Deposited By: George Porter
Deposited On:14 Feb 2017 15:36
Last Modified:11 Nov 2021 05:26

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