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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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