Polarimetry plays an important role in investigating physical properties for celestial objects. We present a polarimeter named YFPOL for the Cassegrain focus of the Lijiang 2.4 m Telescope (LJT) of Yunnan Observatories, Chinese Academy of Sciences. YFPOL is a traditional single-beam polarimeter with a rotating polarizer. As the focal-reducer instrument Yunnan Faint Object Spectrograph and Camera (YFOSC) is always positioned on the Cassegrain focal plane of LJT, we develop two sets of ultra-thin (thickness<12 mm) polarizer rotation control systems with wireless charging and control functions, which are suitable for mounting on the two front-wheels of YFOSC. One set is used as the polarimetric calibration unit, and the other is for the polarimetric modulation unit. Both of the polarizers have an ultra-high contrast ratio of 1,000,000:1 in the optical band. We investigate the instrumental polarization characteristics (IPCs) in the full field of view that is transferred from YFOSC. Furthermore, we identify that the IPCs change when the Cassegrain axis rotates. The spurious polarization from the IPCs can be effectively minimized by flat-fielding using the unpolarized domeflat, when the Cassegrain rotation angle is the same or nearest to that of the polarization observation. We develop a quasi-automatic pipeline for YFPOL and its effectiveness has been verified by tests of the polarimetric observation with blazar S50716+714. The calibration is performed by observing the zero-polarized and highly-polarized standard stars. We successfully reach high precision polarization in the 7￠ field of view, and the systematic uncertainty is below 0.8％for a V=11.68 target with a 10 s exposure. The instrument polarization angle offset is 2°. 6. YFPOL is not only a simple polarimeter, but also a spectropolarimeter with grisms that can be considered in the future.

Yu-Xin Xin;Jin-Ming Bai;Zhong-Quan Qu;Zhi Xu;Ji-Rong Mao;Kai Ye;Bao-Li Lun;Xu Ding;Hong-Tao Liu;Yue Zhong;Yu-Feng Fan;Xiao-Guang Yu;Liang Xu;Xiao-Bo Dong;Jian-Guo Wang;Ding-Rong Xiong

Yunnan Observatories,Chinese Academy of Sciences,Kunming 650216,China;University of Chinese Academy of Sciences,Beijing 100049,China;Key Laboratory for the Structure and Evolution of Celestial Objects,Chinese Academy of Sciences,Kunming 650216,China;Center for Astronomical Mega-Science,Chinese Academy of Sciences,Beijing 100012,China

天文和天体物理学研究

[1]Yu-Xin Xin;Jin-Ming Bai;Zhong-Quan Qu;Zhi Xu;Ji-Rong Mao;Kai Ye;Bao-Li Lun;Xu Ding;Hong-Tao Liu;Yue Zhong;Yu-Feng Fan;Xiao-Guang Yu;Liang Xu;Xiao-Bo Dong;Jian-Guo Wang;Ding-Rong Xiong-.YFPOL:A Linear Polarimeter of Lijiang 2.4 m Telescope)[J].天文和天体物理学研究,2022(09):10-34

YFPOL,Polarimeter,Polarimetry,Cassegrain,Observatories,Faint,YFOSC,fielding,domeflat,blazar,S50716+714,spectropolarimeter,grisms

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