A discussion on metallicity effects on the period-luminosity relations of Cepheids and Miras
A discussion on metallicity effects on the period-luminosity relations of Cepheids and Miras
复制标题
金属丰度对造父变星和米拉斯周期光度关系影响的讨论
DOI：
10.1007/s10509-012-1090-x
复制
发表时间：
2012
影响因子：
1.9
通讯作者：
Matsunaga
中科院分区：
文献类型：
--
作者：
田中克典;深瀬浩一;M. Nakamura;Matsunaga
经典造父变星和Miras的周期光度关系（以下简称PLR）是重要的距离指标，但未解决的金属丰度效应仍然是不确定性的关键来源。由于越来越多的证据表明金属丰度效应明显小于光学波段，近红外（IR）波段的PLR变得非常重要。我们最近的近红外观测显示，除了先前已知的米拉星之外，银河系中心还有经典的造父变星。另一方面，麦哲伦云中的这些类型的变量已经在光学引力透镜实验（OGLE）中得到了很好的搜索，并且存在包括这些物体的近红外目录。这使我们能够直接比较不同环境中的距离指标。在这里，我们比较了经典造父变星和富氧的米拉在银河系中心和大，小麦哲伦云的近红外PLR。这样，我们就可以在相对意义上讨论金属丰度对PLR的影响，而不需要知道恒星系统的真实距离。我们发现，金属丰度对造父变星logP-K关系的影响，如果有的话，是类似于Miras的情况下，0.1等的限制，当我们比较这些对象在麦哲伦云。
The period-luminosity relations (hereafter PLRs) of classical Cepheids and Miras are important distance indicators, but the unsolved metallicity effects remain as a critical source of uncertainty. The PLRs in the near infrared (IR) bands have become important due to the increasing evidence for significantly smaller metallicity effects than in the optical bands. Our recent near-IR survey revealed classical Cepheids, in addition to previously known Miras, in the Galactic Centre. On the other hand, these types of variables in the Magellanic Clouds have been well searched for in the Optical Gravitational Lensing Experiment (OGLE), and there exist near-IR catalogues which include those objects. These allow us a direct comparison of the distance indicators found in different environments. Here we compare the near-IR PLRs of classical Cepheids and oxygen-rich Miras in the Galactic Centre and the Large and Small Magellanic Cloud. In this way, we can discuss the metallicity effects on their PLRs, in a relative sense, without the knowledge of the true distances to the stellar systems. We found that the metallicity effect on the logP–Ksrelation of Cepheids, if any, is similar to the case of Miras, to the limit of 0.1 mag when we compare these objects in the Magellanic Clouds.