OJ_Astro, New Publication at the Open Journal of Astrophysics: "A 1.9 solar-mass neutron star candidate in a 2-year orbit" by Kareem El-Badry (Caltech, USA) and 12 others based in the USA, Germany, Chile, Denmark and Israel.
https://astro.theoj.org/article/116675-a-1-9-solar-mass-neutron-star-candidate-in-a-2-year-orbit