Theoretical Study of i-process Contribution to the Post-AGB Star IRAS 14325-6428
5 affiliations
- 1Chinese Academy of Sciences
- 2University of Chinese Academy of Sciences
- 3Inner Mongolia Minzu University
- 4Inner Mongolia Joint Key Laboratory of Nuclear and Radiation Detection
- 5China Institute of Atomic Energy
Abstract
The post-asymptotic giant branch (post-AGB) star IRAS 14325-6428 exhibits a peculiar heavy-element abundance pattern, characterized by a high [Ba/La] ratio and an anomalous odd-isotope Ba ratio ( f odd,Ba = 0.25 ± 0.08), which is difficult to explain via the classical slow neutron-capture process ( s -process). We theoretically investigate this abundance pattern by considering the intermediate neutron-capture process ( i -process) nucleosynthesis. The i -process nucleosynthesis calculations are performed with a one-zone network (NucNet Tools) at constant temperature and density, using intershell abundances obtained from a stellar model (1.5 M ⊙ , Z = 0.003) evolved with MESA to the thermally pulsing AGB phase. The observed heavy-element abundances are best reproduced by a model with neutron density N n = 5 × 10 ¹³ cm ⁻³ and neutron exposure τ = 1.4 mbarn ⁻¹ , followed by dilution with a scaled-solar composition. This model reproduces the high [Ba/La] and [Ba/Ce] ratios and yields a postdilution odd-isotope fraction f odd,Ba ≈ 0.51, which is supported by the observed value being substantially above the expectations of the pure s -process. The abundance pattern arises from the i -process path approaching the neutron magic number N = 82, where the flow slows, and the material accumulates at ¹³⁵ I, which subsequently β ⁻ decays to ¹³⁵ Ba, enhancing Ba production and reducing the synthesis of heavier species. Combined with its multielement i -process classification, our results provide quantitative support for a dominant i -process origin of the heavy elements in IRAS 14325−6428, likely triggered by a relatively short-lived proton-ingestion episode in its AGB progenitor.
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BibTeX
@article{li2026theoretical,
title = {{Theoretical Study of i-process Contribution to the Post-AGB Star IRAS 14325-6428}},
author = {Guo Li and Jian-Rong Shi and Su-Ya-La-Tu Zhang and Hong-Liang Yan and Yong-Shou Chen},
journal = {The Astrophysical Journal},
year = {2026},
month = nov,
doi = {10.3847/1538-4357/aeb015},
url = {https://iopscience.iop.org/article/10.3847/1538-4357/aeb015},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Theoretical Study of i-process Contribution to the Post-AGB Star IRAS 14325-6428
AU - Guo Li
AU - Jian-Rong Shi
AU - Su-Ya-La-Tu Zhang
AU - Hong-Liang Yan
AU - Yong-Shou Chen
PY - 2026
DA - 2026/11/05
JO - The Astrophysical Journal
DO - 10.3847/1538-4357/aeb015
UR - https://iopscience.iop.org/article/10.3847/1538-4357/aeb015
AB - The post-asymptotic giant branch (post-AGB) star IRAS 14325-6428 exhibits a peculiar heavy-element abundance pattern, characterized by a high [Ba/La] ratio and an anomalous odd-isotope Ba ratio ( f odd,Ba = 0.25 ± 0.08), which is difficult to explain via the classical slow neutron-capture process ( s -process). We theoretically investigate this abundance pattern by considering the intermediate neutron-capture process ( i -process) nucleosynthesis. The i -process nucleosynthesis calculations are performed with a one-zone network (NucNet Tools) at constant temperature and density, using intershell abundances obtained from a stellar model (1.5 M ⊙ , Z = 0.003) evolved with MESA to the thermally pulsing AGB phase. The observed heavy-element abundances are best reproduced by a model with neutron density N n = 5 × 10 ¹³ cm ⁻³ and neutron exposure τ = 1.4 mbarn ⁻¹ , followed by dilution with a scaled-solar composition. This model reproduces the high [Ba/La] and [Ba/Ce] ratios and yields a postdilution odd-isotope fraction f odd,Ba ≈ 0.51, which is supported by the observed value being substantially above the expectations of the pure s -process. The abundance pattern arises from the i -process path approaching the neutron magic number N = 82, where the flow slows, and the material accumulates at ¹³⁵ I, which subsequently β ⁻ decays to ¹³⁵ Ba, enhancing Ba production and reducing the synthesis of heavier species. Combined with its multielement i -process classification, our results provide quantitative support for a dominant i -process origin of the heavy elements in IRAS 14325−6428, likely triggered by a relatively short-lived proton-ingestion episode in its AGB progenitor.
SN - 1538-4357
SN - 0004-637X
ER -