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| Paper: |
Testing the Dust Shell Model for Long Secondary Period AGB Stars |
| Volume: |
497, Why Galaxies Care about AGB Stars III: A Closer Look in Space and Time |
| Page: |
403 |
| Authors: |
Takayama, M.; Wood, P. R.; Ita, Y. |
| Abstract: |
Using long-term JHKs light curves and OGLE V and I light curves, we examine the variability of two AGB stars in the Small Magellanic Cloud (SMC) which show a Long Secondary Period (hereafter, LSP). The origin of the LSPs is currently unknown. We find that in the oxygen-rich stars the J–Ks color hardly changes and sometimes becomes bluer when the luminosity of the star declines during its LSP cycle, although other colors (e.g. V–I and I–J) get redder. This implies that H2O vapor absorption increases when the light declines due to the development of a layer of dense cool gas in the stellar photosphere. The development of a chromosphere between minimum and maximum light has been reported by previous observations. Those results suggest that, as one possibility, the variability of AGB stars with LSP is associated with the ejection of matter from the photosphere. We explore the possibility that broadband light variations from optical to near IR associated with the LSP phenomenon can be explained by dust absorption by ejected matter. |
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