Oxygen Line Diagnostics in X-ray spectroscopy

Line diagnostics is very important to understand the physics of astronomical sources. Taking advantage of oxygen line diagnostics in X-ray spectroscopy, I will show some of our research for both the moderate-resolution the high-resolution X-ray spectra based on the newly updated atomic database (ATOMDB). I will demonstrate its power for SgrA spectrum, HII regions, and some nearby galaxies. In addition, I will introduce related space mission concepts in China, which we are currently proposing.