II型造父变星原型室女W的多色测光
Multicolor photometry of the Type II Cepheid prototype W Virginis
摘要：
我们提出了最近的长期BVRcIc光度监测II型造父变星原型W室女座的结果。在2006年和2007年的观测季节中，这些新的观测结果代表了迄今为止最长的西维尔均匀的光变曲线。BVRcIc的光和颜色曲线最终表明，W Vir表现出适度的，但可检测的周期到周期的变化，其原因似乎是多周期性，而不是非线性。我们将我们的V波段数据与ASAS-3 V波段测光的五个可用年份相结合，获得了一个6.5年的光变曲线，然后我们分析了该光变曲线，获得了W Vir的脉动光谱。我们找到了一个最佳拟合周期P（0）= 17.27134 d;除了这个周期及其整数谐波，我们还清楚地检测到另外两个周期P（1）和P（low），它们分别接近但不完全是2 P（0）/3和2 P（0）。前者P（1）= 11.52562 d，我们认为是第一泛音模，后者P（low）= 34.59760 d，与P（0）和P（1）的拍周期以及2 P（0）的值接近。我们解释以前报道的，但迄今未经证实的描述交替极小作为这种多周期性的表现。最后，我们利用V波段光变曲线的周期定义了一个新的星历表：HJD（max）= 2452758.172 + 17.27134E。使用1932年至2007年75年的数据得到的（O-C）图产生的星历周期变化项为-9.9乘以10（-7）E^（2），表明周期减小。
英文摘要：
We present the results of recent long-term BVRcIc photometric monitoring of the type II Cepheid prototype W Virginis. These new observations, made during the 2006 and 2007 observing season, represent the longest homogeneous, multicolor light curve of W Vir to date. The BVRcIc light and color curves show conclusively that W Vir exhibits modest but detectable cycle-to-cycle variations, the cause of which appears to be multiperiodicity rather than nonlinearity. We combined our V-band data with the five available years of ASAS-3 V-band photometry to obtain a 6.5-year light curve that we then analyzed to obtain the pulsation spectrum of W Vir. We find a best-fit period P(0) = 17.27134 d; along with this period and its integer harmonics, we clearly detect two additional periods, P(1) and P(low), that are close to but not exactly 2P(0)/3 and 2P(0), respectively. The former, P(1) = 11.52562 d, we interpret to be the first overtone mode; the latter, P(low) = 34.59760 d is close to the beat period of P(0) and P(1), as well as to the value of 2P(0). We interpret the previously reported but thus far unconfirmed descriptions of alternating minima as manifestations of this multiperiodicity. Finally, we use the period derived from the V-band light curve to define a new ephemeris: HJD(max) = 2452758.172 + 17.27134E. The resulting (O-C) diagram using 75 years of data from 1932 to 2007 yields a period change term for the ephemeris of -9.9 times 10(-7) E^(2), indicating a period decrease.
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