探索CoRoT靶HD 49933中p模频移的来源
Exploring the sources of p-mode frequency shifts in the CoRoT target HD 49933
摘要：
类太阳恒星HD 49933的振荡已经被CoRot彻底观测到。测量了与磁活动变化密切相关的两打频移。为了探讨磁活动对频移的影响，我们用一般变分法计算了HD 49933的径向和$l = 1$ p模的频移，该方法利用核和一些源的乘积的空间积分来计算频移.理论上的频移很好地再现了观测结果。根据$χ^2$准则确定源的幅度和位置。我们预测的源，有助于$l = 0$和$l = 1$模式位于$0.48 - 0.62$毫米以下的恒星表面。此外，基于$A_{0}$与Mg II活性指数$Δ{i}_{MgII}$的变化成比例的假设，我们得到HD 49933循环周期的最小值和最大值之间的Mg II指数变化约为0.665。与太阳相比，HD 49933的频移幅度已经告诉我们，HD 49933比太阳活跃得多，这在本文中得到了进一步证实。此外，我们对$l = 1$模频移的计算表明，恒星对流区湍流速度的变化可能是导致$l = 1$模频移的一个重要原因。
英文摘要：
The oscillations of the solar-like star HD 49933 have been observed thoroughly by CoRot. Two dozens of frequency shifts, which are closely related with the change in magnetic activity, have been measured. To explore the effects of the magnetic activity on the frequency shifts, we calculate frequency shifts for the radial and $l = 1$ p-modes of HD 49933 with the general variational method, which evaluates the shifts using a spatial integral of the product of a kernel and some sources. The theoretical frequency shifts well reproduce the observation. The magnitudes and positions of the sources are determined according to the $χ^2$ criterion. We predict the source that contributes to both $l = 0$ and $l = 1$ modes is located at $0.48 - 0.62$Mm below the stellar surface. In addition, based on the assumption that $A_{0}$ is proportional to the change in the MgII activity index $Δ{i}_{MgII}$, we obtained that the change of MgII index between minimum and maximum of HD 49933 cycle period is about 0.665. The magnitude of the frequency shifts compared to the Sun already told us that HD 49933 is much more active than the Sun, which is further confirmed in this paper. Furthermore, our calculation on the frequency shifts of $l = 1$ modes indicates the variation of turbulent velocity in the stellar convective zone may be an important source for the $l = 1$ shifts.
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