标题： 造父变星振幅的观测研究。 I - 银河系造父变星的周期-振幅关系以及振幅的相互关系 显示英文标题

标题： Observational studies of Cepheid amplitudes. I - Period-amplitude relationships for Galactic Cepheids and interrelation of amplitudes

摘要： 目的：我们试图基于多色测光和径向速度数据修订银河系造父变星的周期-振幅（P-A）关系。为U、B、V、R_C 和 I_C 光学波段构建可靠的造父变星周期-振幅图，并研究脉动径向速度变化，有助于探索之前研究较少的可观测振幅之间的相互关系。 结果：具有伴星的大振幅造父变星的平均光度振幅比单星的小，正如预期的那样，而s-型造父变星以任意但较小的振幅脉动。观测径向速度与蓝光光度振幅的比值A_V_RAD/A_B 并非如理论预测的那样是脉动模式的良好指标。这可能是由于对一些小振幅造父变星的模态分配错误，这些恒星不一定是一阶过调制脉动器。利用脉动振幅随波长的变化来识别造父变星的双重性。超过二十颗之前被归类为孤立造父变星的恒星现在被认为可能有伴星。在不同波段观测到的光度振幅比率证实了正常振幅造父变星之间存在二分法。短周期和长周期造父变星的分界线周期为10.47天。 结论：脉动振幅的相互依赖性、振幅参数的周期依赖性以及二分法必须作为造父变星结构和脉动建模的约束条件加以考虑。P-L关系的研究必须符合10.47天的断裂点，而不是目前使用的“方便”的10天值。 显示英文摘要

摘要： Aims: We attempt to revise the period-amplitude (P-A) relationship of Galactic Cepheids based on multi-colour photometric and radial velocity data. Reliable P-A graphs for Galactic Cepheids constructed for the U, B, V, R_C, and I_C photometric bands and pulsational radial velocity variations facilitate investigations of previously poorly studied interrelations between observable amplitudes. The effects of both binarity and metallicity on the observed amplitude, and the dichotomy between short- and long-period Cepheids can both be studied. Results: Large amplitude Cepheids with companions exhibit smaller photometric amplitudes on average than solitary ones, as expected, while s-Cepheids pulsate with an rbitrary (although small) amplitude. The ratio of the observed radial velocity to blue photometric amplitudes, A_V_RAD/A_B, is not as good an indicator of the ulsation mode as predicted theoretically. This may be caused by an incorrect mode assignment to a number of small amplitude Cepheids, which are not ecessarily first overtone pulsators. The dependence of the pulsation amplitudes on wavelength is used to identify duplicity of Cepheids. More than twenty stars previously classified as solitary Cepheids are now suspected to have a companion. The ratio of photometric amplitudes observed in various bands confirms the existence of a dichotomy among normal amplitude Cepheids. The limiting period separating short- and long-period Cepheids is 10.47 days. Conclusions: Interdependences of pulsational amplitudes, the period dependence of the amplitude parameters, and the dichotomy have to be taken into account as constraints in modelling the structure and pulsation of Cepheids. Studies of the P-L relationship must comply with the break at 10.47 instead of the currently used `convenient' value of 10 days.