猎户座$\bpi^5$椭球SPB变星的BRITE星座测光
BRITE-Constellation photometry of $\bpi^5$ Orionis, an ellipsoidal SPB variable
摘要：
本文给出了SB 1系统和椭球变星$π^5$ Ori（B2，III）的BRITE星座测光分析结果。除了轨道光变化，它可以表示为频率为$f_{\rm orb}$，$2f_{\rm orb}$，$3f_{\rm orb}$，$4f_{\rm orb}$和$6f_{\rm orb}$的五项傅立叶余弦级数，其中$f_{\rm orb}$是系统的轨道频率，该恒星显示出五个低振幅但高度显著的正弦变化，频率为$f_i$（$i ={}$ 2，..，5，7）在0.16 ~ 0.92 dPDMATHABMU范围内。在精度优于1 $σ$的情况下，后者的频率遵循以下关系：$f_2-f_4 = 2f_{\rm orb}$、$f_7 - f_3 = 2f_{\rm orb}$、$f_5 = f_3 - f_4 = f_7 - f_2$。我们解释前两个关系的证据表明，两个高阶$\ell = 1, m = 0$重力模式是自激系统的潮汐扭曲的主要组成部分。这颗恒星是一颗椭圆形的SPB变星。最后的关系产生于两个模式之间的一阶微分组合项的存在。基本参数，来自文献中的光度数据和{ \em依巴谷\/}视差，表明主要组成部分是接近其主序列（MS）演化的终端阶段。广泛的Wilson-Devinney模型得出的结论是，最适合的理论观察到的光变曲线获得的有效温度和质量与主要的HR图中的位置相一致，并表明次级是在早期MS的进化阶段。
英文摘要：
Results of an analysis of the BRITE-Constellation photometry of the SB1 system and ellipsoidal variable $π^5$ Ori (B2\,III) are presented. In addition to the orbital light-variation, which can be represented as a five-term Fourier cosine series with the frequencies $f_{\rm orb}$, $2f_{\rm orb}$, $3f_{\rm orb}$, $4f_{\rm orb}$ and $6f_{\rm orb}$, where $f_{\rm orb}$ is the system's orbital frequency, the star shows five low-amplitude but highly-significant sinusoidal variations with frequencies $f_i$ ($i ={}$2,..,5,7) in the range from 0.16 to 0.92~d$^{-1}$. With an accuracy better than 1$σ$, the latter frequencies obey the following relations: $f_2-f_4 = 2f_{\rm orb}$, $f_7 - f_3 = 2f_{\rm orb}$, $f_5 = f_3 - f_4 = f_7 - f_2$. We interpret the first two relations as evidence that two high-order $\ell = 1, m = 0$ gravity modes are self-excited in the system's tidally distorted primary component. The star is thus an ellipsoidal SPB variable. The last relations arise from the existence of the first-order differential combination term between the two modes. Fundamental parameters, derived from photometric data in the literature and the {\em Hipparcos\/} parallax, indicate that the primary component is close to the terminal stages of its main sequence (MS) evolution. Extensive Wilson-Devinney modeling leads to the conclusion that best fits of the theoretical to observed light-curves are obtained for the effective temperature and mass consistent with the primary's position in the HR diagram and suggests that the secondary is in an early MS evolutionary stage.
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