Discrimination of background events in the PolarLight X-ray polarimeter  

作　　者：Jiahuan Zhu Hong Li Hua Feng Jiahui Huang Xiangyun Long Qiong Wu Weichun Jiang Massimo Minuti Saverio Citraro Hikmat Nasimi Dongxin Yang Jiandong Yu Ge Jin Ming Zeng Peng An Luca Baldini Ronaldo Bellazzini Alessandro Brez Luca Latronico Carmelo Sgrò Gloria Spandre Michele Pinchera Fabio Muleri Paolo Soffitta Enrico Costa 

机构地区：[1]Department of Astronomy,Tsinghua University,Beijing 100084,China [2]Department of Engineering Physics,Tsinghua University,Beijing 100084,China [3]Key Laboratory for Particle Astrophysics,Institute of High Energy Physics,Chinese Academy of Sciences,Beijing 100049,China [4]INFN-Pisa,Largo B.Pontecorvo 3,56127 Pisa,Italy [5]School of Electronic and Information Engineering,Ningbo University of Technology,Ningbo 315211,China [6]North Night Vision Technology Co.,Ltd.Nanjing 211106,China [7]INFN,Sezione di Torino,Via Pietro Giuria 1,1-10125 Torino,Italy [8]IAPS/INAF,Via Fosso del Cavaliere 100,00133 Rome,Italy

出　　处：《Research in Astronomy and Astrophysics》2021年第9期202-206,共5页天文和天体物理学研究（英文版）

基　　金：funding support from the National Natural Science Foundation of China(Grant Nos.11633003,12025301 and 11821303);the CAS Strategic Priority Program on Space Science(Grant No.XDA15020501-02);the National Key R&D Project(Grant Nos.2018YFA0404502 and 2016YFA040080X)。

摘　　要：PolarLight is a space-borne X-ray polarimeter that measures the X-ray polarization via electron tracking in an ionization chamber.It is a collimated instrument and thus suffers from the background on the whole detector plane.The majority of background events are induced by high energy charged particles and show ionization morphologies distinct from those produced by X-rays of interest.Comparing on-source and off-source observations,we find that the two datasets display different distributions on image properties.The boundaries between the source and background distributions are obtained and can be used for background discrimination.Such a means can remove over 70%of the background events measured with PolarLight.This approaches the theoretical upper limit of the background fraction that is removable and justifies its effectiveness.For observations with the Crab nebula,the background contamination decreases from 25%to 8%after discrimination,indicative of a polarimetric sensitivity of around 0.2 Crab for PolarLight.This work also provides insights into future X-ray polarimetric telescopes.

关 键 词：instrumentation:polarimeters methods:data analysis X-rays:general 

分 类 号：P172.2[天文地球—天文学]