标题： CD-27 11535: Evidence for a Triple System in the $β$ Pictoris Moving Group 显示英文标题

标题： CD-27 11535: Evidence for a Triple System in the $β$ Pictoris Moving Group

摘要： 我们展示了对CD-27 11535系统的新的空间分辨视差测量和测光数据，该系统是$\beta$南鱼座运动星群的成员，由两个分开的K型恒星组成，轨道周期为$\sim$20年。 我们使用NIRC2、GPI和NaCo档案图像以及文献中的测量值拟合了相对视差轨道。然而，从这个轨道推断出的总质量与使用两颗恒星亮度推断的质量存在显著差异。 我们探讨了两种可能解释这一质量差异的原因：由于变异性导致的Gaia视差测量偏差，以及两组分之一存在额外未分辨伴星。我们发现，$\sim$20年的轨道不会影响视差测量，但分量的变异性可能会产生较大的天体测量运动，而这种运动的幅度无法通过Gaia的个体测量精确量化。 该差异也可能由系统内额外的一颗恒星解释。我们将系统的天体测量和测光数据联合拟合，以测试不同双星和三合星结构的可能性。根据所使用的演化模型集，我们发现包括一颗低质量($M=0.177\pm0.055$ $M_{\odot}$)主星伴星的三合星结构具有更好的拟合优度。 为了消除这一差异，需要对该系统进行进一步研究，可以通过更复杂的变异性引起的天体测量运动处理来改进视差测量，或者通过探测第三颗伴星来实现。 显示英文摘要

摘要： We present new spatially resolved astrometry and photometry of the CD-27 11535 system, a member of the $\beta$ Pictoris moving group consisting of two resolved K-type stars on a $\sim$20-year orbit. We fit an orbit to relative astrometry measured from NIRC2, GPI, and archival NaCo images, in addition to literature measurements. However, the total mass inferred from this orbit is significantly discrepant from that inferred from stellar evolutionary models using the luminosity of the two stars. We explore two hypotheses that could explain this discrepant mass sum; a discrepant parallax measurement from Gaia due to variability, and the presence of an additional unresolved companion to one of the two components. We find that the $\sim$20-year orbit could not bias the parallax measurement, but that variability of the components could produce a large amplitude astrometric motion, an effect which cannot be quantified exactly without the individual Gaia measurements. The discrepancy could also be explained by an additional star in the system. We jointly fit the astrometric and photometric measurements of the system to test different binary and triple architectures for the system. Depending on the set of evolutionary models used, we find an improved goodness of fit for a triple system architecture that includes a low-mass ($M=0.177\pm0.055$\,$M_{\odot}$) companion to the primary star. Further studies of this system will be required in order to resolve this discrepancy, either by refining the parallax measurement with a more complex treatment of variability-induced astrometric motion, or by detecting a third companion.