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| Paper: |
An Explanation of the Observed Dip at 8-10 Days in the Galactic Cepheid Period Histogram |
| Volume: |
135, A Half Century of Stellar Pulsation Interpretations: a Tribute to Arthur N. Cox |
| Page: |
285 |
| Authors: |
Goupil, M. J.; Buchler, J. R.; Beaulieu, J. P. |
| Abstract: |
The Galactic Cepheid period histogram has a two-humped shape with a strong minimum between 8 ans 10 days that cannot be reproduced with combined evolutionary and linear pulsation studies. Numerical hydrodynamical calculations show that the lack of Cepheids in this period range arises because the corresponding finite amplitude oscillations in the fundamental radial mode are not stable- and therefore cannot exist- for the Galactic mean metallicity of Z~0.02. This instability of the fundamental limit cycle disappears for low enough metallicities. The existence of a dip rather than a total absence of 8-10d Galactic Cepheids in the periodogram therefore suggests that the Galactic Cepheids have a large spread in metallicity. The strong metallicity dependence of the instability also explains the absence of a similar minimum in the Cepheid period histogram of the less metallic Magellanic Clouds. |
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