发表机构
Korea Astronomy and Space Science Institute; Chungbuk National University（韩国天文学与空间科学研究所; 忠北国立大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究综合测光与光谱分析，揭示相接双星BS Cas的星斑驱动光变及第三体存在，证实轨道周期衰减与角动量损失相关。
AI 中文摘要
我们基于22年的多站点光变曲线和2年的高分辨率光谱，对相接食双星BS Cas进行了全面的测光和光谱分析。长期测光显示出光变曲线形状逐年显著变化，包括主次极小之间食深反转以及O'Connell效应的变化。利用展宽函数（BF）轮廓从光谱中首次推导出BS Cas的双线径向速度（RV）曲线。2018年BF中缺失的尖锐峰出现在2020年BF中，表明存在与BS Cas同视线方向的额外成分。对BVR光变曲线和RV的同时建模表明，BS Cas是一个相接双星，其中质量较大的成分比质量较小的伴星更冷，质量比为2.515，填充因子为32.3%。多历元建模表明，长期光变变化源于演化中的星斑和第三光贡献的变化。食时变化图证实了轨道周期以$-2.305 \times 10^{-7}~\mathrm{天\\,年^{-1}}$的速率长期减小，与角动量损失和质量转移一致，同时存在18.376年的调制，被解释为来自第三体的光行时效应。TESS计时显示主次极小之间存在反相关变化，这似乎源于高纬度星斑的较差自转。这些结果表明，BS Cas是一个物理上复杂的相接双星，其长期测光和食时变化反映了多种过程，包括磁活动和第三体的影响。
英文摘要
We present a comprehensive photometric and spectroscopic analysis of the contact eclipsing binary BS Cas, based on 22-yr multi-site light curves and 2-yr high-resolution spectra. The long-term photometry shows pronounced year-to-year changes in the light-curve shape, including eclipse-depth reversals between the primary and secondary minima and variations in the O'Connell effect. The first double-lined radial-velocity (RV) curves of BS Cas are derived from the spectra using broadening-function (BF) profiles. Sharp peaks absent from the 2018 BFs appear in the 2020 BFs, suggesting an additional component along the same line of sight as BS Cas. Simultaneous modeling of the BVR light curves and the RVs shows that BS Cas is a contact binary in which the more massive component is cooler than its less massive companion, with a mass ratio of 2.515 and a fill-out factor of 32.3%. Multi-epoch modeling suggests that the long-term photometric variations arise from evolving starspots and changes in the third-light contribution. The eclipse-timing variation diagram confirms a secular orbital period decrease at a rate of $-2.305 \times 10^{-7}~\mathrm{days\,yr^{-1}}$ consistent with angular momentum loss and mass transfer, along with an 18.376-yr modulation interpreted as a light-travel-time effect from a third body. The TESS timings reveal anti-correlated variations between the primary and secondary minima that appear to result from differential rotation of high-latitude starspots. These results suggest that BS Cas is a physically complex contact binary in which long-term photometric and eclipse-timing variations reflect multiple processes, including magnetic activity and the influence of a third body.
CommentsAccepted for publication in The Astronomical Journal
