Russian astronomers have performed a detailed study of one of the ultraluminous X-ray sources (ULXs) in the galaxy UGC 6456. Results of the research, presented in a paper published November 20 on arXiv.org, suggest that this source, designated UGC 6456 ULX, is one of the brightest known ULXs in the optical range.
Source:
https://phys.org/news/2019-11-ultraluminous-x-ray-source-ugc-ulx.html