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| Main Authors: | , |
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| Format: | Preprint |
| Published: |
2025
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/2502.08842 |
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Table of Contents:
- At least a third of red giants show a long secondary period (LSP), 5 to 10 times longer than the pulsation period. There is strong evidence that the LSP is caused by eclipses of the red giant by a dust-enshrouded low-mass companion. We have used long-term AAVSO observations of 11 stars to study two aspects of the eclipse hypothesis: the relation between the LSP phase (eclipse) curve and the geometry of the eclipse, and the long-term (decades) changes in the LSP phenomenon in each star. The stars with the largest LSP amplitudes show evidence of a dust tail on the companion, but most of the 11 stars show only a small-amplitude sinusoidal phase curve. The LSP amplitudes of all the stars vary slowly by up to a factor of 8, suggesting that the amount of obscuring dust varies by that amount, but there is no strong evidence that the geometry of the system changes over many decades.