造父变星北极星回归：从地面和太空监测4.5年
Polaris the Cepheid returns: 4.5 years of monitoring from ground and space
摘要：
我们提出了4.5年的经典造父变星北极星，其中包括最精确的数据，这颗星几乎连续观测的分析。我们已经从地面进行了光谱测量，并从WIRE星跟踪仪和科里奥利卫星上的SMEI仪器进行了光度测量。对主振荡（P = 4天）振幅的测量可以追溯到一个多世纪以前，显示在千年之交从120毫等（V等）下降到30毫等。据推测，振幅减小的原因是北极星向不稳定带边缘演化。然而，我们的新数据显示，从2003年到2006年，振幅增加了约30%。现在看来，振幅变化是周期性的，而不是单调的，很可能是脉动现象的结果。此外，以前的径向速度活动声称探测到北极星的长周期变化（P > 40天）。我们的径向速度数据比以前的数据集更精确，并且我们没有发现3-50天范围内的额外变化的证据，上限为100 m/s。然而，在WIRE数据中，我们发现了2-6天时间尺度变化的证据，我们将其解释为由于造粒。
英文摘要：
We present the analysis of 4.5 years of nearly continuous observations of the classical Cepheid Polaris, which comprise the most precise data available for this star. We have made spectroscopic measurements from ground and photometric measurements from the WIRE star tracker and the SMEI instrument on the Coriolis satellite. Measurements of the amplitude of the dominant oscillation (P = 4 days), that go back more than a century, show a decrease from 120 mmag to 30 mmag (V magnitude) around the turn of the millennium. It has been speculated that the reason for the decrease in amplitude is the evolution of Polaris towards the edge of the instability strip. However, our new data reveal an increase in the amplitude by about 30% from 2003-2006. It now appears that the amplitude change is cyclic rather than monotonic, and most likely the result of a pulsation phenomenon. In addition, previous radial velocity campaigns have claimed the detection of long-period variation in Polaris (P > 40 days). Our radial velocity data are more precise than previous datasets, and we find no evidence for additional variation for periods in the range 3-50 days with an upper limit of 100 m/s. However, in the WIRE data we find evidence of variation on time-scales of 2-6 days, which we interpret as being due to granulation.
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