Search for gamma-ray bursts and gravitational wave electromagnetic counterparts with High Energy X-ray Telescope of <i>Insight</i>-HXMT
Ce Cai, S. L. Xiong, Cheng-Kui Li, Chao‐Zong Liu, S N Zhang, Xiaobing Li, L. M. Song, Bing Li, Shuo Xiao, Q. B. Yi, Yiming Zhu, Y. G. Zheng, Wei Chen, Q. Luo, Y. Huang, X. Y. Song, Haisheng Zhao, Y. Zhao, Z. H. Zhang, Qingcui Bu, X. L. Cao, Zhi Chang, Lei Chen, Tao Chen, Y B Chen, Ye Chen, Yupeng Chen, Wei Cui, Yong Du, G. H. Gao, H. Gao, Mingyu Ge, Yun-Jun Gu, Ju Guan, Chengcheng Guo, D. W. Han, J. Huo, S. M. Jia, Weichun Jiang, Jing Jin, Ling-Da Kong, Gongjie Li, Ting Li, Wenfei Li, Xue Li, X F Li, Zhifeng Li, X. H. Liang, J. Y. Liao, B S Liu, Hanwei Liu, H X Liu, Xiaoyu Liu, F. J. Lu, Xiao-Meng Lu, T. Luo, Ruican Ma, Xiang Ma, Bin Meng, Y. Nang, J. Y. Nie, G. Ou, Jin‐Lu Qu, Xiaoqin Ren, Na Sai, Liang Sun, Y. Tan, Lian Tao, Y. L. Tuo, Chen‐Zhu Wang, Ling‐Jun Wang, Peng-Ju Wang, W S Wang, Y S Wang, X. Y. Wen, Bobing Wu, Bai-Yang Wu, Mei‐Hwan Wu, G. Xiao, Y. P. Xu, Yi-Jung Yang, Shengqi Yang, H. J. Yang, Yushu Yang, Xuejuan Yang, Qian-Qing Yin, Yuan You, Fan Zhang, Hongming Zhang, J. Zhang, Peng Zhang, S Zhang, W C Zhang, W Zhang, Y F Zhang, Y H Zhang, Xiao-Yun Zhao, S. J. Zheng, D. K. Zhou
Abstract
ABSTRACT The High Energy (HE) X-ray telescope on board the Hard X-ray Modulation Telescope (Insight-HXMT) can serve as a wide field of view (FOV) gamma-ray monitor with high time resolution (μs) and large effective area (up to thousands cm2). We developed a pipeline to search for gamma-ray bursts (GRBs), using the traditional signal-to-noise ratio (SNR) method for blind search and the coherent search method for targeted search. By taking into account the location and spectrum of the burst and the detector response, the targeted coherent search is more powerful to unveil weak and sub-threshold bursts, especially those in temporal coincidence with gravitational wave (GW) events. Based on the original method in literature, we further improved the coherent search to filter out false triggers caused by spikes in light curves, which are commonly seen in gamma-ray instruments (e.g. Fermi/GBM, POLAR). We show that our improved targeted coherent search method could eliminate almost all false triggers caused by spikes. Based on the first two years of Insight-HXMT/HE data, our targeted search recovered 40 GRBs, which were detected by either Swift/BAT or Fermi/GBM but too weak to be found in our blind search. With this coherent search pipeline, the GRB detection sensitivity of Insight-HXMT/HE is increased to about 1.5E-08 erg cm−2 (200 keV–3 MeV). We also used this targeted coherent method to search Insight-HXMT/HE data for electromagnetic counterparts of LIGO-Virgo GW events (including O2 and O3a runs). However, we did not find any significant burst associated with GW events.