roAp α星Circini的星震分析：来自WIRE卫星的84天高精度测光
Asteroseismic analysis of the roAp star alpha Circini: 84 days of high-precision photometry from the WIRE satellite
摘要：
我们提出了一个详细的研究脉动的α Circini，最明亮的快速振荡的Ap星。我们已经获得了84天的高精度测光，从四个运行与线卫星上的恒星跟踪器。与此同时，我们在南非天文台收集了16个晚上的地面约翰逊B观测数据。除了在2442微赫兹的主导振荡模式，我们检测到两个新的模式，对称地躺在周围的主模式，形成一个三重态。这些模式之间的平均间隔为30.173 ± 0.004微赫兹，它们几乎是等距的，间隔仅相差3.9毫赫兹。我们比较观察到的频率与理论脉动模型的基础上，从最近确定的干涉半径和有效温度的约束，以及最近更新的依巴谷视差。我们发现，理论上的大分离α Cir模型与全球参数内的1西格玛观测不确定性在59和65微赫兹之间变化。这与观测值的两倍的大分离是一致的，表明三个主要模式是交替的偶数和奇数度。在三重态的频率差是显着小于从我们的模型预测的，为所有可能的模式度的组合，并可能表明，磁扰动的影响需要考虑在内。WIRE的光变曲线是由一个周期为4.479天的双波调制的，峰间振幅为4毫等。这种变化是由于恒星的旋转，是一个新的发现，由于WIRE测光的高精度而成为可能。旋转调制证实了旋转周期的早期间接确定。
英文摘要：
We present a detailed study of the pulsation of alpha Circini, the brightest of the rapidly oscillating Ap stars. We have obtained 84 days of high-precision photometry from four runs with the star tracker on the WIRE satellite. Simultaneously, we collected ground-based Johnson B observations on 16 nights at the South African Astronomical Observatory. In addition to the dominant oscillation mode at 2442 microHz, we detect two new modes that lie symmetrically around the principal mode to form a triplet. The average separation between these modes is 30.173+-0.004 microHz and they are nearly equidistant with the separations differing by only 3.9 nHz. We compare the observed frequencies with theoretical pulsation models based on constraints from the recently determined interferometric radius and effective temperature, and the recently updated Hipparcos parallax. We show that the theoretical large separations for models of alpha Cir with global parameters within the 1-sigma observational uncertainties vary between 59 and 65 microHz. This is consistent with the large separation being twice the observed value, indicating that the three main modes are of alternating even and odd degrees. The frequency differences in the triplet are significantly smaller than those predicted from our models, for all possible combinations of mode degrees, and may indicate that the effects of magnetic perturbations need to be taken into account. The WIRE light curves are modulated by a double wave with a period of 4.479 days, and a peak-to-peak amplitude of 4 mmag. This variation is due to the rotation of the star and is a new discovery, made possible by the high precision of the WIRE photometry. The rotational modulation confirms an earlier indirect determination of the rotation period.
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