In this talk, I will introduce the background of 3.5 keV line, then focus on the debate(including Dessert et al. Science(2020), arXiv 2004.06170; 2004.06601; 2006.03974) for 3.5 keV line signal in 2020.
Finally, Lei Lei(雷磊) hope to spend several minutes showing his roughly results in this talk, which using M87@HXMT and M31@Chandra data. What is worth mentioning, Lei Lei is an brilliant undergraduate in Yunnan University, whose bachelor thesis is investigating 3.5 keV emission line.