The mass-luminosity relation is a fundamental law of astrophysics. We have suggested that the currently used mass-luminosity relation is not correct for the M/M_sun > 2.7 range of mass since it was created using double-lined eclipsing binaries, where the components are synchronized and consequently change each other's evolutionary path. To exclude this effect we have started a project to study long-period massive eclipsing binaries in order to construct radial velocity curves and determine masses for the components. We outline our project and present the selected test sample together with the first HRS/SALT spectral observations and the software package, FBS (Fitting Binary Stars), that we developed for the analysis of our spectral data. As the first result we present the radial velocity curves and best-fit orbital elements for the two components of the FP Car binary system from our test sample.

中文翻译：

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长周期食双星：走向真正的质光关系。一、测试样本、观察和数据分析

质光关系是天体物理学的基本定律。我们已经提出，当前使用的质量-光度关系对于 M/M_sun > 2.7 质量范围是不正确的，因为它是使用双线食双星创建的，其中组件是同步的，因此会改变彼此的进化路径。为了排除这种影响，我们启动了一个研究长期大规模食双星的项目，以构建径向速度曲线并确定组件的质量。我们概述了我们的项目，并将选定的测试样本与第一个 HRS/SALT 光谱观测结果和我们为分析光谱数据而开发的软件包 FBS（拟合双星）一起展示。