Probing Red Giant Interiors with g-Dominated Mixed Modes II: The Cases of KIC 6117517, KIC 9475697, KIC 10123207 and KIC 10200377
Abstract
Building on Paper~I, which constrained core overshooting to fov < 0.01 for M < 1.4 M⊙ and found αMLT ≃ 2.0 for metal-rich red giants, we extend this analysis to four lower-mass \textit{Kepler} red giants spanning a broad metallicity range: KIC~6117517, KIC~9475697, KIC~10123207, and KIC~10200377. Two complementary model grids are constructed: Grid~A fixes αMLT = 2.0 while varying metallicity; Grid~B adopts spectroscopic metallicities with αMLT as a free parameter. Grid~A successfully reproduces both asteroseismic and spectroscopic constraints for the metal-rich targets (KIC~6117517 and KIC~9475697), confirming αMLT = 2.0 for metal-rich red giants. For the metal-poor targets (KIC~10123207 and KIC~10200377), Grid~B yields larger mixing-length parameters of αMLT ≈ 2.16--$2.18$. Although only four stars are analyzed with unequal sensitivity to αMLT, these results suggest a tentative increase in convective efficiency toward lower metallicity, consistent with 3D hydrodynamical simulations but opposite to some 1D empirical calibrations. The best-fitting overshooting parameters (fov = 0.006--$0.007$) independently support the Paper~I constraint and are consistent with a mass-dependent overshooting relation. The parameter uncertainties reach $0.6−−2.5\%$ in mass, $0.2−−0.9\%$ in radius, $2−−13\%$ in age, and below 0.6% in helium-core mass and below 0.2% in helium-core radius. Surface-effect corrections are negligible for g-dominated mixed modes, validating χ2l=1g as a robust fitting metric. For KIC~9475697, the core rotation rate is determined to be Ωcore = 0.6945 ± 0.0190 μHz from model-based trapping parameters.
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BibTeX
@misc{zhang2026probing,
title = {{Probing Red Giant Interiors with g-Dominated Mixed Modes II: The Cases of KIC 6117517, KIC 9475697, KIC 10123207 and KIC 10200377}},
author = {Xinyi Zhang and Tanda Li and Shaolan Bi},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.32357},
eprint = {2610.32357},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.32357},
}
RIS
TY - UNPB
TI - Probing Red Giant Interiors with g-Dominated Mixed Modes II: The Cases of KIC 6117517, KIC 9475697, KIC 10123207 and KIC 10200377
AU - Xinyi Zhang
AU - Tanda Li
AU - Shaolan Bi
PY - 2026
DA - 2026/10/23
PB - arXiv
DO - 10.48550/arxiv.2610.32357
UR - https://arxiv.org/abs/2610.32357
AB - Building on Paper~I, which constrained core overshooting to f_ov < 0.01 for M < 1.4 M_⊙ and found α_MLT ≃ 2.0 for metal-rich red giants, we extend this analysis to four lower-mass \textit{Kepler} red giants spanning a broad metallicity range: KIC~6117517, KIC~9475697, KIC~10123207, and KIC~10200377. Two complementary model grids are constructed: Grid~A fixes α_MLT = 2.0 while varying metallicity; Grid~B adopts spectroscopic metallicities with α_MLT as a free parameter. Grid~A successfully reproduces both asteroseismic and spectroscopic constraints for the metal-rich targets (KIC~6117517 and KIC~9475697), confirming α_MLT = 2.0 for metal-rich red giants. For the metal-poor targets (KIC~10123207 and KIC~10200377), Grid~B yields larger mixing-length parameters of α_MLT ≈ 2.16--$2.18$. Although only four stars are analyzed with unequal sensitivity to α_MLT, these results suggest a tentative increase in convective efficiency toward lower metallicity, consistent with 3D hydrodynamical simulations but opposite to some 1D empirical calibrations. The best-fitting overshooting parameters (f_ov = 0.006--$0.007$) independently support the Paper~I constraint and are consistent with a mass-dependent overshooting relation. The parameter uncertainties reach $0.6−−2.5\%$ in mass, $0.2−−0.9\%$ in radius, $2−−13\%$ in age, and below 0.6% in helium-core mass and below 0.2% in helium-core radius. Surface-effect corrections are negligible for g-dominated mixed modes, validating χ^2_l=1g as a robust fitting metric. For KIC~9475697, the core rotation rate is determined to be Ω_core = 0.6945 ± 0.0190 μHz from model-based trapping parameters.
ER -