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Paper: Why Variable AGB Stars with Long Secondary Periods Aren't Binaries, but Are Dusty
Volume: 445, Why Galaxies Care about AGB Stars II: Shining Examples and Common Inhabitants
Page: 167
Authors: Nicholls, C.
Abstract: Roughly 30% of variable AGB stars show a Long Secondary Period, or LSP. These LSPs have posed something of a problem in recent years and their cause remains a mystery. By combining VLT–derived velocity curves with MACHO and OGLE light curves, we have been able to examine many properties of these stars and test the theory that LSPs are caused by binarity. We show why we conclude that the binary model for LSPs is unlikely. Examining mid-infrared SAGE observations for stars with LSPs shows that these stars are surrounded by significant amounts of cool dust in a non-spherical distribution, e.g. a disk or clumps. The unlikeliness of binarity in these stars forces us to conclude that the dust is not in a disk. We are left without an acceptable explanation for Long Secondary Periods in AGB stars.
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