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arXiv · 1212.0549

Semiregular variables with periods lying between the period-luminosity sequences C', C and D

I. Soszynski·P. R. Wood
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Abstract

We analyze the distribution of semiregular variables and Mira stars in the period-luminosity plane. Our sample consists of 6169 oxygen-rich long-period variables in the Large Magellanic Cloud included in the OGLE-III Catalog of Variable Stars. There are many stars with periods that lie between the well known sequences C and C'. Most of these stars are multi-periodic and the period ratios suggest that these stars oscillate in the same mode as the sequence C stars. Models suggest that this mode is the fundamental radial pulsation mode. The stars with primary periods between sequences C and C' preferentially lie on an additional sequence (named F), and a large fraction of these stars also have long secondary periods that lie between sequences C and D. There are also a small number of stars with primary periods lying between sequences C and D. The origin of this long period variability is unknown, as is the cause of sequence D variability. In addition, the origin of sequence F is unknown but we speculate that sequence F variability may be excited by the same phenomenon that causes the long secondary periods.

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I. Soszynski, P. R. Wood. 2012-12-03. Semiregular variables with periods lying between the period-luminosity sequences C', C and D. https://doi.org/10.1088/0004-637x%2F763%2F2%2F103

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