This subject is up on the Thunderblogs this week, presumably pre-emted by the new study. At https://phys.org/news/2020-05-black-holes-neutron-stars-merge.html … mergers between black holes and neutron stars. They say they occur in dense star clusters. The hope is that by studying this phenomenon they will find info on gravitational waves. Thunderblogs didn't put it in quite the same way.
At https://phys.org/news/2020-05-reveal-common-fermi-galactic-center.html … a pair of enormous gamma ray bubbles in the centre of the Milky Way were discovered by the Fermi Gamma Ray Space Telescope ten years ago. How they arose is a mystery. Recently, a new study by a Chinese university claims to have discovered how. It is an explanation but will it last the course is another matter. They combine the gamma ray bubbles with biconical x-rays (also discovered at the galactic centre). It involves a massive outburst from a black hole. What does it mean if black holes do not exist?