AI 中文总结
研究在Subaru/SCExAO/CHARIS的Nasmyth光束切换器升级后更新偏振校准，提出考虑升级部件的模型，对比新旧模型精度，分析各部件偏振效应，给出校准代码，可提高偏振精度并便于未来重新校准。
AI 中文摘要
Subaru/SCExAO/CHARIS可实现近红外积分场光谱偏振测量。定量偏振测量对多种科学案例有用，特别是与恒星周盘尘埃颗粒特性相关的测量。此功能需通过穆勒矩阵模型校正光路的偏振效应。我们提出一个更新模型，考虑了最近安装的SCExAO近红外波前传感器YJH50分色镜和Subaru Nasmyth光束切换器的主要升级。通过光束切换器安装前后的内部光源测量，发现图像旋转器的椭圆延迟器模型比之前的线性延迟器模型提高了偏振精度。还发现YJH50分色镜产生微弱偏振效应，而Nasmyth光束切换器除了在Q和V偏振光中引起符号翻转外，偏振效应最小。通过非偏振标准星校准测量，拟合了Subaru第三反射镜的二向色性随波长的变化，发现自上次CHARIS校准以来二向色性增加。计算得出该模型在1%偏振目标的线性偏振度方面的偏振精度为0.02%至0.12%。此模型更新将很快纳入CHARIS数据处理管道，应在2025年10月Nasmyth光束切换器更新后用于任何偏振数据。此外，我们提供了该校准代码作为名为pyPolCal的开源Python偏振校准包的一部分，以便在未来任何变化（如M3最近重新镀膜）后能直接重新校准系统。
英文摘要
Subaru/SCExAO/CHARIS enables near-infrared integral field spectropolarimetry. Quantitative polarimetry is useful for a variety of science cases, particularly measurements related to dust grain properties in circumstellar disks. This capability requires correcting for polarization effects from the optical path via a Mueller matrix model. We present an updated model accounting for the recently installed SCExAO near-infrared wavefront sensor YJH50 dichroic beamsplitter and the major Subaru Nasmyth beam-switcher upgrade. Using internal light source measurements from before and after the beam switcher installation, we find an elliptical retarder model for the image derotator improves polarimetric accuracy over the previous linear retarder model. We additionally find the YJH50 dichroic produces faint polarization effects that we cannot characterize with our Mueller matrix modeling capabilities, and that the Nasmyth beam-switcher has minimal polarization effects other than inducing a sign flip in Q and V polarized light. Using unpolarized standard star calibration measurements, we fit the diattenuation of Subaru's tertiary mirror as a function of wavelength and find that the diattenuation has increased since the previous CHARIS calibration. We calculate that the polarimetric accuracy of the model in the degree of linear polarization ranges from 0.02% to 0.12% for a 1% polarized target. This model update will soon be incorporated into CHARIS's data processing pipeline, and should be used for any polarimetric data taken after the Nasmyth beam-switcher update in October 2025. Additionally, we provide the code for this calibration as part of an open-source Python package for polarimetric calibration called pyPolCal, enabling straightforward re-calibration of the system after any future changes, e.g. the recent recoating of M3.
CommentsSubmitted to SPIE Astronomical Telescopes + Instrumentation 2026
