W UMa型系统LO Andromedae特征的新研究
A new investigation on the characteristics of a W UMa type system LO Andromedae
AI总结：
本研究通过多晚观测与数据分析，更新了W UMa型系统LO And的恒星参数，发现其周期加速增加，归因于系统内质量转移及可能存在的第三颗恒星引起的光时效应。
摘要：
本研究在达勒姆对W Ursae Majoris（W UMa）型系统LO Andromedae（LO And）进行了九个夜晚的观测，以全面探究其物理性质并更新恒星参数。获取V滤镜和B滤镜的观测数据后，使用Linux命令从Astrolab内部档案中提取了LO And的Gaia CCD图像。通过应用“Nightfall”程序和本地Python脚本，可绘制、相位折叠和拟合LO And的校准光变曲线，得出该系统的周期为$0.3804573 \pm 0.0000482\\\\, \mathrm{d}$。随后，绘制了二维卡方热图以确定LO And的最佳拟合恒星参数并估计其不确定性，包括质量比$q = 0.371 \pm 0.207$、倾角$i = 78.5 \pm 3.8\\\\, \mathrm{deg}$、主星温度$T_1 = 6290 \pm 358\\\\, \mathrm{K}$、次星温度$T_2 = 6449 \pm 445\\\\, \mathrm{K}$，以及两个填充因子$f_1 = f_2 = 1.02258$。此外，“Nightfall”程序构建了3D模型并评估了黑子分布参数，以可视化LO And的结构。本研究新增了七个食变计时数据，结合LO And之前的观测数据重建了O-C图。研究明确发现，LO And的周期目前正加速增加，变化率为$d\mathrm{P}/d\mathrm{t} = 2.27 \times 10^{-7}\\\\, \mathrm{day\\\\, yr^{-1}}$，这归因于该系统中的质量转移（转移率$dM_1/d\mathrm{t} = 1.43 \times 10^{-7}\\\\, \mathrm{M_\odot\\\\, yr^{-1}}$）以及可能存在的环绕LO And的第三颗恒星（$M_3 = 0.224\\\\, M_\odot$）引起的光时效应。
英文摘要：
In this study, a W Ursae Majoris (W UMa) type system LO Andromedae (LO And) was observed over nine nights at Durham to fully investigate its physical properties and update its stellar parameters. After obtaining the observational data in both V-filter and B-filter, the Gaia CCD images of LO And were extracted from the Astrolab internal archive using Linux commands. By applying the "Nightfall" program and local Python scripts, the calibrated light curves of LO And can be plotted, phase-folded, and fitted to derive the period of this system as $0.3804573 \pm 0.0000482\, \mathrm{d}$. Then, 2D chi-squared heat maps were illustrated to determine LO And's best-fit stellar parameters and estimate their uncertainties, including the mass ratio $q = 0.371 \pm 0.207$, the inclination $i = 78.5 \pm 3.8\, \mathrm{deg}$, the primary temperature $T_1 = 6290 \pm 358\, \mathrm{K}$, the secondary temperature $T_2 = 6449 \pm 445\, \mathrm{K}$, and two fill factors $f_1 = f_2 = 1.02258$. In addition, the "Nightfall" program built the 3D models and evaluated the spot distribution parameters to visualize the configuration of LO And. There were seven new eclipsing timings added in this study to reconstruct the O-C diagram together with LO And's previous observational data. It was clearly found that the period of LO And is currently undergoing an accelerated increase with a change rate $d\mathrm{P}/d\mathrm{t} = 2.27 \times 10^{-7}\, \mathrm{day\, yr^{-1}}$, which was attributed to the mass transfer in this system with a transfer rate $dM_1/d\mathrm{t} = 1.43 \times 10^{-7}\, \mathrm{M_\odot\, yr^{-1}}$ and the light time effect caused by the possible existence of a third star $M_3 = 0.224\, M_\odot$ orbiting around LO And.
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