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| Paper: |
The Dynamic Atmospheres of Mira Stars: Comparing the CODEX
Models to PTI Time Series Observations of TU Andromedae |
| Volume: |
497, Why Galaxies Care about AGB Stars III: A Closer Look in Space and Time |
| Page: |
117 |
| Authors: |
Hillen, M.; Verhoelst, T.; Degroote, P.; Acke, B.; Van Winckel, H. |
| Abstract: |
We present our already-published evaluation of the effectiveness of
the CODEX models, released in 2011, in representing the atmospheres
of M-type Mira variables. We present a high-precision interferometric
K-band time series of TU And, consisting of 50 nights that cover
eight consecutive pulsation cycles. At each phase, the flux at
2.2μm was obtained, along with the spectral shape and visibility
points in five channels across the K band. We show a comparison
between these data and the dynamical self-excited CODEX model which
gives the closest match in stellar parameters yet available. Both the
spectrum and the visibilities are consistently reproduced around visual
minimum phases. Near the maximum phases, however, the current models
predict a photosphere that is too hot and compact, surrounded by an
extended atmosphere that lacks H2O opacity, compared to the
observations. A better coverage in the model parameter space is needed
to make firm conclusions as to the cause of the discrepancies. In the
case of TU And, the discrepancy might be lifted by adopting a lower
value of the mixing length parameter combined with an increased stellar
mass and/or a decreased metallicity. |
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