Issue |
A&A
Volume 689, September 2024
|
|
---|---|---|
Article Number | A111 | |
Number of page(s) | 10 | |
Section | Stellar atmospheres | |
DOI | https://doi.org/10.1051/0004-6361/202451052 | |
Published online | 06 September 2024 |
Secular stability of surface abundance structures in the rapidly rotating Ap star 56 Ari
1
Institute of Astronomy of RAS,
Pyatnitskaya str., 48,
119017
Moscow,
Russia
2
Department of Physics and Astronomy, Division of Astronomy and Space Physics, Uppsala University,
PO Box 516,
751 20
Uppsala,
Sweden
Received:
10
June
2024
Accepted:
12
July
2024
The combination of the surface magnetic and abundance inhomogeneities in chemically peculiar Ap/Bp stars is responsible for their rotationally modulated variability. Within the framework of the fossil field hypothesis, these inhomogeneities are considered to be essentially stable over the main sequence timescale. However, a small group of Ap/Bp stars show rotational period changes that are not fully understood. Here, we present results of Doppler imaging of the rapidly rotating Ap star 56 Ari whose changes in period had previously been detected. A reconstruction of the surface distribution of silicon in 56 Ari reveals its complex spot pattern, which is responsible for the rotationally light variability and is correlated with a magnetic field modulation. Comparisons of abundance maps obtained over the unprecedentedly long (for such studies) interval from 1986 to 2014 confirms the stability and rigid rotation of the spot pattern. Thus, we find the period change in 56 Ari is not caused by a rearrangement of the surface magnetic structures and/or atomic diffusion operating on short timescale. It is also unlikely to be explained by the visibility changes of the spots due to the free-body precession of the stellar rotational axis. We briefly discuss possible alternative explanations of the period variability.
Key words: stars: chemically peculiar / stars: individual: 56 Ari / starspots
© The Authors 2024
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.
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