On the Cepheid Metallicity Dichotomy - AstrophysicsReport as inadecuate

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Abstract: With the aid of stellar atmosphere models, we derive iron abundances Fe-Hfrom the OGLE B, V, I photometry on the Magellanic Cloud Cepheids. We show thatin both clouds the average metallicities of the first overtone variables arelower than those of the fundamental ones by ~0.2 and ~0.3 dex in the LMC andSMC, respectively. Consequently, there is a correlation between the overallFe-H and luminosity; the lower luminosity stars tend to be also of lowermetallicity. These metallicity dependencies are concordant with the onesderived for the two types of double-mode Cepheids from pulsation theory. Yetanother support of this dichotomy comes from the evolution theories thatrequire lower metallicities for blue-looping low-luminosity stars than forhigh-luminosity ones. We also comment on the possibility of usingperiod-luminosity-color relations to derive more accurate metallicities.

Author: Geza Kovacs

Source: https://arxiv.org/

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