标题： 关于RR lyrae变星的调制频率分布 显示英文标题

标题： On the distribution of the modulation frequencies of RR Lyrae stars

摘要： 首次检测到了造父变星（RR Lyrae）脉动与调制属性之间的联系。根据现有数据发现，调制频率的可能范围，即调制频率的最大可能值取决于脉动频率。短周期变量（P < 0.4 天）可以具有短至几天的调制周期，而长周期变量（P > 0.6 天）总是表现出调制周期 P_mod > 20 天。我们用调制周期等于表面自转周期来解释这一趋势，因为如果恒星离开红巨星分支（RGB）时总角动量存在上限，则预计会得到类似的自转周期分布。不同温度下红群和蓝群水平分支星投影自转速度的分布显示了与从造父变星调制周期推导出的 v_rot 相似的特性。这种共同行为使得我们可以将调制周期识别为调制造父变星的自转周期。 显示英文摘要

摘要： For the first time connection between the pulsation and modulation properties of RR Lyrae stars has been detected. Based on the available data it is found that the possible range of the modulation frequencies, i.e, the possible maximum value of the modulation frequency depends on the pulsation frequency. Short period variables (P < 0.4 d) can have modulation period as short as some days, while longer period variables (P > 0.6 d) always exhibit modulation with P_mod > 20 d. We interpret this tendency with the equality of the modulation period with the surface rotation period, because similar distribution of the rotational periods is expected if an upper limit of the total angular momentum of stars leaving the RGB exists. The distribution of the projected rotational velocities of red and blue horizontal branch stars at different temperatures shows a similar behaviour as v_rot derived for RR Lyrae stars from their modulation periods. This common behaviour gives reason to identify the modulation period with the rotational period of the modulated RR Lyrae stars.