造父变星周期-光度关系的斜率
Concerning the Slope of the Cepheid Period-Luminosity Relation
摘要：
我们讨论的造父变星周期亮度关系的斜率的可能差异的影响，在最近的研究表明，在这个斜率的变化的背景下，确定河外距离。我们表明，Wesenchman函数W = V-R x（（V-I），广泛用于确定造父变星的距离，预计是高度不敏感的基础（单色）周期-亮度（PL）关系的斜率的变化。这是因为在颜色-星等平面中的红化轨迹与等周期线紧密平行。因此，基于W的周期光度关系具有极低的残余色散，这是因为在W的定义中消除了微分（和总视线）红化，并且由于造父变星内的固有颜色/位置而产生的残余散射也对W不敏感。基本方程和图形说明，显示的不敏感性W的单色PL关系的变化。
英文摘要：
We discuss the impact of possible differences in the slope of the Cepheid Period-Luminosity relation on the determination of extragalactic distances in the context of recent studies that suggest changes in this slope. We show that the Wesenheit function W = V - R x ((V-I), widely used for the determination of Cepheid distances, is expected to be highly insensitive to changes in the slope of the underlying (monochromatic) Period-Luminosity (PL) relations. This occurs because the reddening trajectories in the color-magnitude plane are closely parallel to lines of constant period. As a result W-based Period-Luminosity relations have extremely low residual dispersion, which is because differential (and total line-of-sight) reddening is eliminated in the definition of W and the residual scatter due to a star's intrinsic color/position within the Cepheid is also largely insensitive to W. Basic equations are presented and graphically illustrated, showing the insensitivity of W to changes in the monochromatic PL relations.
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