Stellar evolution along the AGB as revealed by the shape of Miras' visual light curves
| Autor: | Hoai, D. T., Nhung, P. T., Darriulat, P., Tan, M. N. |
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| Rok vydání: | 2024 |
| Předmět: | |
| Druh dokumentu: | Working Paper |
| Popis: | A new analysis of a sample of visual light curves of Long Period Variable (LPV) Mira stars is presented. The curves cover the past four decades and are selected from the AAVSO data base as including a very large number of high-density and high-quality observations. The aim of the analysis is to offer a more precise, more quantitative and more systematic picture than available from earlier studies. The results corroborate earlier descriptions and reveal new correlations between the shapes of the light curves and the time spent by the star on the Asymptotic Giant Branch (AGB). A family of nearly sinusoidal curves, associated with M-type spectral types and displaying no sign of having entered the thermally-pulsing phase (TP-AGB) is identified with good confidence. All other curves are clearly distinct from this family and usually start departing from it by displaying a broader luminosity minimum, implying a slowing down of the rate of luminosity increase on the ascending branch. This slowing down feature, referred to as a hump, spans across the ascending branch as the spectral-type of the star evolves from M to C. It may go all the way to maximal light or stop earlier, covering only part of the ascending branch. While this general average trend is established with good confidence, deviations from it cause a significant scatter of the parameters defining the shapes of the curves. Comments aimed at shedding light on the underlying physics are presented together with speculative interpretations, in the hope that they could encourage and inspire new studies, in particular based on simulations using state-of-the-art models of the inner star dynamics. Comment: 29 pages, 22 figures |
| Databáze: | arXiv |
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