Be星NW Ser和V1446 Aql的多周期脉动
Multiperiodic pulsations in the Be stars NW Ser and V1446 Aql
摘要：
目的：给出两颗Be星NW Ser和V1446 Aql的精确光度时间序列。2003年7月，内华达山脉天文台（格拉纳达）用自动四通道斯特伦格伦光度计观测到这两颗恒星。我们还提出了一个初步的理论研究表明，这些恒星所表现出的周期性变化可能是由于脉动。方法：一个详尽的傅立叶分析与最小二乘拟合已进行了所有四个Strömgren波段的时间序列。几个独立的频率和非周期性的趋势解释了大部分的变化。一个理论上的非绝热代码适用于这些恒星的恒星模型表明，g-模式是不稳定的。结果：这两颗恒星的振幅都有快速的变化，可能是由于拍频现象。每颗恒星都有四个显著的频率。比较所观察到的振幅比，为每个脉动频率与理论脉动代码计算，使我们能够估计与不同的检测频率的脉动模式。NW Ser似乎也显示出不稳定的p模，因此可能是新发现的$β$仙王座和SPB混合星之一。计划进一步进行光谱观测，以研究探测到的频率的稳定性。
英文摘要：
Aims: We present accurate photometric time series of two Be stars: NW Ser and V1446 Aql. Both stars were observed at the Observatorio de Sierra Nevada (Granada) in July 2003 with an automatic four-channel Strömgren photometer. We also present a preliminary theoretical study showing that the periodic variations exhibited by these stars can be due to pulsation. Methods: An exhaustive Fourier analysis together with a least-square fitting has been carried out on the time series for all four Strömgren bands. Several independent frequencies and non-periodic trends explain most of the variance. A theoretical non-adiabatic code applied to stellar models for these stars shows that g-modes are unstable. Results: Both stars show rapid variations in amplitude, probably due to a beating phenomenon. Four significant frequencies have been detected for each star. Comparison of the observed amplitude ratios for each pulsational frequency with those calculated from theoretical pulsation codes allows us to estimate the pulsation modes associated with the different detected frequencies. NW Ser seems also to show unstable p-modes and thus could be one of the newly discovered $β$ Cephei and SPB hybrid stars. Further spectroscopic observations are planned to study the stability of the detected frequencies.
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