We study relations of the parameter R_var (amplitude of the brightness variability, stellar activity indicator) with respect to the effective temperature and the period of rotation of stars belonging to the A–M spectral types. A common dataset gives an idea of variations in this parameter for stars with convection. It was confirmed that the limit of applicability for the gyrochronological relation PtM does not correspond to the limiting value (B - V )₀ 0.47, and the relationship between a rotation period and color is likewise visible up to groups of stars with (B - V )₀ = 0.2. It is shown that the value of the parameter R_var for stars with effective temperatures of 6500–7500 K are about an order of magnitude lower than that for stars, which indicates a nonmonotonic change of the parameter and, therefore, does not allow us to conclude that there is a single dependence of this parameter in the entire temperature range. In the diagram R_var–P (the rotation period), A-type stars fall in the sequence of fast-rotating active objects, whereas stars with similar temperatures and belonging to the F spectral type (including objects from the cluster NGC 6866) lie in a different sequence corresponding to fast-rotating objects with a small amplitude in the brightness variability. The existence of a unified relationship between the properties of rotational activity in stars of spectral types A, F, and later, as well as possible physical processes leading to the implementation of a standard gyrochronological ratio and activity in A stars are discussed.

中文翻译：

---

A–M星的亮度变化幅度的变化

我们研究了参数R _var（亮度变化的幅度，恒星活动指标）相对于有效温度和属于A–M光谱类型的恒星自转周期的关系。一个通用的数据集给出了对流恒星该参数变化的想法。可以确定的是，对时间序列关系PtM的适用范围与极限值（B-V）₀ 0.47不对应，并且自转周期和颜色之间的关系在（B-V）₀ = 0.2。显示参数R _var的值对于有效温度为6500–7500 K的恒星，它的质量大约比恒星低一个数量级，这表明该参数是非单调变化的，因此，我们不能得出结论，认为该参数仅存在一个依存关系。整个温度范围。在图中R _var – P（自转周期），A型恒星以快速旋转的活动物体的顺序落入，而温度相似且属于F光谱类型的恒星（包括来自NGC 6866星团的物体）处于与快速变化对应的不同顺序-亮度变化幅度较小的旋转对象。讨论了光谱类型为A，F和以后的恒星中自转活动的特性之间的统一关系，以及导致在A星中实现标准时空比和活动的可能的物理过程。