We present an investigation of the magnetic activity and flare characteristics of the subgiant stars mostly from F and G spectral types and compare the results with the main-sequence (MS) stars. The light curve of 352 stars on the subgiant branch (SGB) from the Kepler mission is analyzed in order to infer stability, relative coverage, and contrast of the magnetic structures and also flare properties using three flare indexes. The results show the following. (i) Relative coverage and contrast of the magnetic features along with rate, power, and magnitude of flares increase on the SGB due to the deepening of the convective zone and more vigorous magnetic field production. (ii) Magnetic activity of the F- and G-type stars on the SGB does not show dependency on the rotation rate and does not obey the saturation regime. This is the opposite of what we saw for the MS, in which the G-, K-, and M-type stars show clear dependency on the Rossby number. (iii) The positive relationship between the magnetic features’ stability and their relative coverage and contrast remains true on the SGB; though, it has a lower dependency coefficient in comparison with the MS. (iv) Magnetic proxies and flare indexes of the SGB stars increase with increasing relative mass of the convective zone.

我们目前主要根据F和G光谱类型对次恒星的磁活动和耀斑特征进行调查，并将结果与​​主序（MS）星进行比较。分析了开普勒任务下的352恒星在亚大分支（SGB）上的光曲线，以便使用三个耀斑指数推断出磁结构的稳定性，相对覆盖率和对比度以及耀斑特性。结果显示如下。（i）由于对流区的加深和更剧烈的磁场产生，SGB上的磁性特征的相对覆盖率和对比度以及速率，功率和耀斑的数量增加。（ii）SGB上的F型和G型恒星的磁活动不显示出对旋转速率的依赖性，并且不服从饱和状态。这与我们在MS中看到的相反，在MS中，G，K和M型恒星表现出对Rossby数的明显依赖性。（iii）磁性特征的稳定性与其相对覆盖率和对比度之间的正相关关系在SGB上仍然成立；但是，与MS相比，它具有较低的依赖性系数。（iv）SGB星的磁代理和耀斑指数随对流区相对质量的增加而增加。