| Issue |
A&A
Volume 701, September 2025
|
|
|---|---|---|
| Article Number | L7 | |
| Number of page(s) | 4 | |
| Section | Letters to the Editor | |
| DOI | https://doi.org/10.1051/0004-6361/202555298 | |
| Published online | 08 September 2025 | |
Letter to the Editor
Off-centre convective zones in mass accreting stellar models
Nicolaus Copernicus Astronomical Centre, Polish Academy of Sciences, Bartycka 18, PL 00-716 Warsaw, Poland
⋆ Corresponding author: amiszuda@camk.edu.pl, amiszuda.astro@gmail.com
Received:
25
April
2025
Accepted:
14
August
2025
We report the physical origin of transient off-centre convective zones (oCZs) that arise in mass accreting stellar models. Using detailed MESA simulations of binary evolution, we find that these oCZs are not numerical artefacts, but emerge due to a local increase in density near the retreating edge of the convective core. The density enhancement raises the local opacity, which amplifies the radiative temperature gradient ∇rad. If this gradient surpasses the Ledoux threshold ∇L, defined by both thermal and compositional stratification, the region becomes convectively unstable. The resulting oCZs are detached from the convective core and transient: mixing within the oCZ erases the local gradient in mean molecular weight and leaves a sharp ∇μ discontinuity at the boundary, thus stabilising the adjacent layers. This mechanism naturally explains the presence and evolution of oCZs, as previously reported in massive interacting stars.
Key words: convection / binaries: close / stars: evolution / stars: interiors
© 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.