半正则变星UZ白羊座可能的空间不对称性
Possible spatial asymmetry in semi-regular variable UZ Arietis
摘要：
半规则变星（英语：Semi-regular variable，SRVs）虽然与Mira变星关系密切，但却是AGB星中研究较少的一类。虽然许多米拉变星的亮度分布不对称是众所周知的，但它只在少数几个SRV中被检测到。在几毫角秒（mas）的亮度分布的不对称性的水平可以检测到高角分辨率的技术，如月球掩星（LO），长基线干涉，孔径掩模干涉。多历元LO观测有可能探测到亮度轮廓偏离球对称。每个LO事件提供了一个统一的磁盘（UD）的角直径沿掩星的位置角。多历元LO观测的UD角直径值的任何显著差异都表示亮度不对称。本文首次报道了在2.2 $μm$上利用LO技术观测到的一个SRV UZ白羊座的三历元UD角直径值。本文还报道了我们最近观测到的光源的光学线偏振。UZ阿里建议的一个小的差异拟合UD值的三个时期的亮度分布的不对称，讨论的背景下所表现出的光源和偏振轴的方向在天空的平面中的光学偏振。
英文摘要：
Semi-regular variables (SRVs) though closely related to Mira variables, are a less studied class of AGB stars. While asymmetry in the brightness distribution of many Mira variables is fairly well known, it is detected only in a few SRVs. Asymmetry in the brightness distribution at the level of a few milliarcsecond (mas) can be detected by high angular resolution techniques like lunar occultations (LO), long baseline interferometry, and aperture masking interferometry. Multi-epoch LO observations have the potential to detect a departure of brightness profile from spherical symmetry. Each LO event provides a uniform disk (UD) angular diameter along the position angle of the occultation. Any significant difference in the UD angular diameter values of multi-epoch LO observations signifies a brightness asymmetry. In this paper, we report for the first time three epoch UD angular diameter values of a SRV UZ Arietis using the LO technique at 2.2 $μm$. Optical linear polarization of the source observed by us recently is also reported. The asymmetric brightness distribution of UZ Ari suggested by a small difference in the fitted UD values for the three epochs, is discussed in the context of optical polarization exhibited by the source and the direction of polarization axis in the plane of the sky.
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