I had a question and I found a thread on PF with a nearly identical question ---Slowly add mass to a neutron star till it collapses. I learned some very interesting physics from that thread, namely the Tolman–Oppenheimer–Volkoff limit, and the significance of "9/8 of its Schwarzschild radius" But I still have my original question. I presume that density would be greater at the core of the neutron star, and that collapse would begin with collapse of the core, blowing away the outermost matter in a manner analogous to a type II supernova. Then the freed outer neutrons would undergo beta decay. Is that reasonable? A second question: presume a stable neutron star that acquires mass and undergoes gravitational collapse. Has astronomy ever observed an event like that?