Issue |
A&A
Volume 695, March 2025
|
|
---|---|---|
Article Number | A249 | |
Number of page(s) | 12 | |
Section | Stellar structure and evolution | |
DOI | https://doi.org/10.1051/0004-6361/202453380 | |
Published online | 25 March 2025 |
Detailed seismic study of Gemma (KIC11026764) using EGGMiMoSA
Unveiling the probing potential of mixed modes for subgiant stars
STAR Institute, Université de Liège, Liège, Belgium
⋆ Corresponding author; martin.farnir@uliege.be
Received:
10
December
2024
Accepted:
5
February
2025
Context. When leaving the main sequence (MS) for the red-giant branch (RGB), subgiant stars undergo fast structural changes. Consequently, their observed oscillation spectra mirror these changes, constituting key tracers of stellar structure and evolution. However, the complexity of their spectra makes their modelling an arduous task, which few authors have undertaken. Gemma (KIC11026764) is a young subgiant with 45 precise oscillation modes observed with Kepler, making it the ideal benchmark for seismic modelling.
Aims. This study is aimed at modelling the subgiant Gemma, taking advantage of most of the precise seismic information available. This approach enables us to pave the way for the seismic modelling of evolved solar-like stars and provide the relevant insights into their structural evolution.
Methods. Using our Levenberg-Marquardt stellar modelling tool, we built a family of models representative of Gemma’s measured seismic indicators obtained via our seismic tool, EGGMiMoSA. We studied the structural information these indicators hold by carefully varying stellar parameters. We also complemented the characterisation with information held by who indicators and non-seismic data.
Results. From the extensive set of models we built and using most of the seismic information at hand, including two ℓ = 1 and one ℓ = 2 mixed modes, we were able to probe the chemical transition at the hydrogen-burning shell. Indeed, we have demonstrated that among our models, only the ones with the sharpest chemical gradient are able to reproduce all the seismic information considered. One possibility to account for such a gradient is the inclusion of a significant amount of overshooting, namely αov = 0.17, which is unexpected for low-mass stars such as Gemma (expected mass of about 1.15 M⊙).
Key words: asteroseismology / stars: abundances / stars: evolution / stars: fundamental parameters / stars: low-mass / stars: solar-type
© The Authors 2025
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
This article is published in open access under the Subscribe to Open model. Subscribe to A&A to support open access publication.
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.