场RR天琴座变星作为银河系探针的应用：IX. 视向速度
On the use of field RR Lyrae as Galactic probes:. IX. Radial velocities
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中文总结 AI 辅助
本研究构建了最大最均匀的场RR天琴座变星视向速度星表，揭示了其视向速度振幅与金属丰度、脉动类型的关系，及Blazhko型变星金属丰度分布特征。
中文摘要 AI 辅助
我们基于自有及公开光谱数据，给出了规模最大、均匀性最佳的场RR天琴座变星（RRL）视向速度（RV）测量星表。样本包含17563颗基频脉动RRL（其中12353颗为RRab型）、5011颗第一谐波段脉动RRL（RRc型），以及199颗双模式脉动RRL（RRd型）。我们利用金属线与巴耳末线的RV曲线（RVC）模板推导RV振幅和γ速度（Vγ，定义为恒星级相对于太阳的RV）。星表的典型精度为：采样充分的RVC平均3.8 km/s，含3-7个相位点的RVC为6.5 km/s，含少于3个相位点的RVC为11.3 km/s。采用不同光谱诊断方法与RVC模板得到的Vγ在误差范围内高度一致。我们发现，金属线的RV振幅金属丰度依赖性可忽略，但Hγ、Hδ的该依赖性随金属丰度升高而增强；测光（V、GBP、G、GRP）与RV振幅的标度关系对RRc型为线性，对RRab型为非线性，且与所用诊断方法无关。该间接证据表明，从不稳定带的蓝色（高温）端到红色（低温）端，对流对光度的影响大于对RV振幅的影响。光谱贝利图（RV振幅与周期的关系）显示，从贫金属到富金属RRL，固定周期处的过渡平滑且离散度降低。最后，我们还发现Blazhko型RRL的金属丰度分布函数偏向金属中等及富金属区间。
英文摘要
We present the largest and most homogeneous catalog of radial velocity (RV) measurements for field RR Lyrae (RRL) variables, based on both proprietary and publicly available spectroscopic data. The sample includes 17,563 RRLs pulsating in the fundamental mode (12,353 RRab), in the first overtone (5,011 RRc), and in double-mode (199 RRd). The RV curve (RVC) templates for metallic and Balmer lines were used to derive RV amplitudes and $V_γ$ velocities, defined as the RV of the stellar barycenter with respect to the Sun. The typical accuracy across the catalog is on average 3.8 km s$^{-1}$ for well-sampled RVCs, 6.5 km s$^{-1}$ for RVCs with 3-7 phase points and 11.3 km s$^{-1}$ for RVCs with fewer than three phase points. The use of different spectroscopic diagnostics and RVC templates provides, within the errors, very similar $V_γ$ velocities. We found that the metallicity dependence of RV amplitudes is vanishing for metallic lines, but becomes increasingly significant for H$γ$ and H$δ$. Moreover, the scaling relations between photometric (V, $G_{BP}$, G, $G_{RP}$) and RV amplitudes are linear for RRc and nonlinear for RRab variables, independently of the adopted diagnostic. This circumstantial evidence indicates that convection affects more luminosity than RV amplitudes when moving from the blue (hot) to the red (cool) edge of the instability strip. The spectroscopic Bailey diagram (RV amplitude versus period) shows a smooth transition and a reduced spread at a fixed period, when moving from metal-poor to metal-rich RRLs. Finally, we also found evidence that the metallicity distribution function of Blazhko RRLs is skewed toward the metal-intermediate and metal-rich regimes.
