论文标题
球状簇NGC 419和SMC场的短期变异性
Short period variability in the globular cluster NGC 419 and the SMC field
论文作者
论文摘要
Delta Scuti（$δ$ SCT）星星在我们的银河系中进行了广泛的研究，但在静脉外系统中却少得多。在这里，我们研究了NGC 419中的$δ$ SCT变量，这是一个中级麦哲伦云（SMC）的中级球状簇（SMC），使用$ G，R，I $ gemini-s/gmos时间序列观测。我们的目标是研究此类变量在群集扩展主序列（MSTO）中的作用。我们报告了在NGC 419场中发现54 $δ$ SCT星和三个黯然失色的二进制文件。我们在NGC 419的MSTO中只发现了$δ$ SCT星的少数，而大多数人却很愚蠢，这表明集群比以前想象的年轻（$ \ lesssim 1.2 $ gyr）。考虑到它们的径向分布，我们仅确定六个$δ$ SCT星是NGC 419的可能成员，而剩余的48个可能是SMC场的$Δ$ SCT星。群集$δ$ SCT恒星似乎靠近MSTO的红色边缘，这支持了扩展MSTO起源于年龄扩散的想法。 48个场$δ$ SCT星星代表了SMC中制造的$δ$ SCT星的最大检测。这些新检测到的$δ$ SCT星的周期分布（0.04 \ Lessim p \ Lessim 0.15 $ d）与其他系统中检测到的相似。幅度分布（$ 0.05 \LessimΔr\ Lessim 0.60 $ mag）可能由于缺乏低振幅星而有偏见。我们最终使用$δ$ SCT星来使用不同的周期稀疏关系来计算距离。获得NGC 419的平均距离模量为$ 18.76 \ PM0.14 $ MAG，对于SMC字段的$ 18.86 \ PM0.11 $ MAG，这与以前的测量相一致。
Delta Scuti ($δ$ Sct) stars have been extensively studied in our Galaxy, but far less in extragalactic systems. Here we study the population of $δ$ Sct variables in NGC 419, an intermediate-age globular cluster of the Small Magellanic Cloud (SMC), using $g,r,i$ Gemini-S/GMOS time series observations. Our goal is to study the role of such variables in the cluster extended main-sequence turnoff (MSTO). We report the discovery of 54 $δ$ Sct stars and three eclipsing binaries in the NGC 419 field. We find only a handful of the $δ$ Sct stars at the MSTO of NGC 419 while the majority is fainter, indicating that the cluster is younger ($\lesssim 1.2$ Gyr) than previously thought. Considering their radial distribution, we identify only six $δ$ Sct stars as probable members of NGC 419 while the 48 remaining are likely $δ$ Sct stars of the SMC field. Cluster $δ$ Sct stars appear close to the red edge of the MSTO, supporting the idea that the extended MSTO has its origin in an age spread. The 48 field $δ$ Sct stars represent the largest detection of $δ$ Sct stars made in the SMC. The period distribution of these newly detected $δ$ Sct stars ($0.04 \lesssim P \lesssim 0.15$ d) is similar to that detected in other systems. The amplitude distribution ($0.05 \lesssim Δr \lesssim 0.60$ mag) is likely biased because of the lack of low-amplitude stars. We finally use the $δ$ Sct stars to calculate distances using different period-luminosity relations. The average distance moduli obtained are $18.76\pm0.14$ mag for NGC 419 and $18.86\pm0.11$ mag for the SMC field, which agree with previous measurements.
