Physical interpretation of the oscillation spectrum on the RGB and AGB
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arXiv
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| Format: | Preprint |
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2025
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| _version_ | 1866908851092062208 |
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| author | Dréau, G. Lebreton, Y. Mosser, B. Stello, D. |
| author_facet | Dréau, G. Lebreton, Y. Mosser, B. Stello, D. |
| contents | The high-frequency resolution of the four-year $\textit{Kepler}$ time series allows detailed study of seismic modes in luminous giants. Seismic observables help infer interior structures via comparisons with stellar models. We aim to investigate differences between H-shell (Red-Giant Branch; RGB) and He-burning (red clump and Asymptotic-Giant Branch; AGB) stars in the He-II ionisation zone and the sensitivity of seismic parameters to input physics in stellar models. We used a grid of stellar models with masses $0.8-2.5M_\odot$ and metallicities $-1.0-0.25$dex, including mass loss, overshooting, thermohaline mixing, and rotation-induced mixing. P-mode frequencies were inferred by suppressing g-modes in the core. The main factors affecting seismic observables are stellar mass and metallicity. The He-II glitch amplitude in the local large frequency separation $Δν$ correlates with the He-II ionisation zone density, explaining observed differences between RGB and clump/AGB stars. That amplitude exceeds 10% of $Δν$ in high-luminosity giants, making the asymptotic expansion less accurate when $Δν\le 0.5\,μ$Hz. Mass loss on the RGB and rotation-induced mixing from the main sequence to the early-AGB produce phase differences in the He-II glitch modulation signature between RGB and clump/AGB stars. Efficient RGB mass loss (for $M \le 1.5\,M_\odot$) and mixing processes (for $M \ge 1.5\,M_\odot$) leave detectable signatures in p-mode frequencies, enabling classification of red giants. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2510_04955 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Physical interpretation of the oscillation spectrum on the RGB and AGB Dréau, G. Lebreton, Y. Mosser, B. Stello, D. Solar and Stellar Astrophysics The high-frequency resolution of the four-year $\textit{Kepler}$ time series allows detailed study of seismic modes in luminous giants. Seismic observables help infer interior structures via comparisons with stellar models. We aim to investigate differences between H-shell (Red-Giant Branch; RGB) and He-burning (red clump and Asymptotic-Giant Branch; AGB) stars in the He-II ionisation zone and the sensitivity of seismic parameters to input physics in stellar models. We used a grid of stellar models with masses $0.8-2.5M_\odot$ and metallicities $-1.0-0.25$dex, including mass loss, overshooting, thermohaline mixing, and rotation-induced mixing. P-mode frequencies were inferred by suppressing g-modes in the core. The main factors affecting seismic observables are stellar mass and metallicity. The He-II glitch amplitude in the local large frequency separation $Δν$ correlates with the He-II ionisation zone density, explaining observed differences between RGB and clump/AGB stars. That amplitude exceeds 10% of $Δν$ in high-luminosity giants, making the asymptotic expansion less accurate when $Δν\le 0.5\,μ$Hz. Mass loss on the RGB and rotation-induced mixing from the main sequence to the early-AGB produce phase differences in the He-II glitch modulation signature between RGB and clump/AGB stars. Efficient RGB mass loss (for $M \le 1.5\,M_\odot$) and mixing processes (for $M \ge 1.5\,M_\odot$) leave detectable signatures in p-mode frequencies, enabling classification of red giants. |
| title | Physical interpretation of the oscillation spectrum on the RGB and AGB |
| topic | Solar and Stellar Astrophysics |
| url | https://arxiv.org/abs/2510.04955 |