DD UMa：Ursa主族成员和BRITE候选者的光谱研究
A Spectroscopic Study of DD UMa: Ursa Major Group Member and Candidate for BRITE
摘要：
大熊座群是一个邻近的恒星超星系团，虽然没有引力约束，但由共同运动的成员定义。DD Uma是一颗$δ$ Scuti恒星，其在大熊座群中的成员身份尚不清楚。这项研究的目的是确认DD Uma在大熊座群中的成员资格，并对该恒星进行详细的光谱分析。由于DD Uma是一颗低振幅的$δ$ Scuti星，我们进行了频率分析。我们确定了基本参数，化学丰度，并推导出恒星的质量和年龄。在本研究中，我们在冈山天文台使用高分辨率摄谱仪HIDES，在2009年2月的$27^{th}$和$4^{th}$ 3月之间观测了DD UMa。为了扩大我们的丰度分析，从EQUIPDIE档案中提取了额外的观察结果。DD UMa的组成员通过检查银河系坐标中恒星的速度来评估。脉动频率通过检查HIDES光谱中的线轮廓变化来确定。恒星的基本参数和化学丰度是通过将合成光谱与HIDES和ESDIE观测结果拟合而得的。根据恒星的空间运动，DD Uma被认为是大熊座星群延伸星流的一员。这是由恒星的化学丰度与大熊座成员一致的支持。这颗恒星被发现是化学太阳，具有$T_{eff}=7450\pm150$ K和$\log g=3.98\pm0.2$。我们发现脉动频率为9.4 c/d和15.0 c/d。虽然这些频率不足以进行星震研究，但DD Uma是BRITE星座未来研究的一颗很好的亮星候选者。
英文摘要：
The Ursa Major group is a nearby stellar supercluster which, while not gravitationally bound, is defined by co-moving members. DD UMa is a $δ$ Scuti star whose membership in the Ursa Major group is unclear. The objective of this study is to confirm the membership of DD UMa in the Ursa Major group, as well as perform a detailed spectral analysis of the star. Since DD UMa is a low-amplitude $δ$ Scuti star, we performed a frequency analysis. We determined fundamental parameters, chemical abundances, and derive a mass and age for the star. For this study we observed DD UMa at the Okayama Astrophysical Observatory with the high-resolution spectrograph HIDES, between the $27^{th}$ of February and the $4^{th}$ March, 2009. Additional observations were extracted from the ELODIE archive in order to expand our abundance analysis. Group membership of DD UMa was assessed by examining the velocity of the star in Galactic coordinates. Pulsational frequencies were determined by examining line profile variability in the HIDES spectra. Stellar fundamental parameters and chemical abundances were derived by fitting synthetic spectra to both the HIDES and ELODIE observations. DD UMa is found to be a member of the extended stream of the Ursa Major group, based on the space motion of the star. This is supported by the chemical abundances of the star being consistent with those of Ursa Major group members. The star is found to be chemically solar, with $T_{eff}=7450\pm150$ K and $\log g=3.98\pm0.2$. We found pulsational frequencies of 9.4 c/d and 15.0 c/d. While these frequencies are insufficient to perform an asteroseismic study, DD UMa is a good bright star candidate for future study by the BRITE-constellation.
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