Discrimination of background events in the PolarLight X-ray polarimeter
Abstract
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.
Keywords
Cite
@article{arxiv.2103.12962,
title = {Discrimination of background events in the PolarLight X-ray polarimeter},
author = {Jiahuan Zhu and Hong Li and Hua Feng and Jiahui Huang and Xiangyun Long and Qiong Wu and Weichun Jiang and Massimo Minuti and Saverio Citraro and Hikmat Nasimi and Dongxin Yang and Jiandong Yu and Ge Jin and Ming Zeng and Peng An and Luca Baldini and Ronaldo Bellazzini and Alessandro Brez and Luca Latronico and Carmelo Sgro and Gloria Spandre and Michele Pinchera and Fabio Muleri and Paolo Soffitta and Enrico Costa},
journal= {arXiv preprint arXiv:2103.12962},
year = {2021}
}
Comments
accepted for publication in Research in Astronomy and Astrophysics