Two articles, one published in the journal “Astronomy and Astrophysics” and one in “The Astrophysical Journal Letter”, describe two researches on the consequences of the merger of two neutron stars detected last year at electromagnetic and gravitational waves. ESA’s XMM-Newton space telescope was used to monitor the evolution of its X-ray emissions. NASA’s Chandra X-ray observatory was similarly used and a team of researchers concluded that the merger generated a black hole.