The Brown researcher thinks the particles are disappearing into the fireball's core and reappearing as thermal radiation, just as matter is thought to fall into a blackhole and come out as "Hawking" radiation.
As Fender explains, however, matter being accreted by the blackhole would swirl down toward its event horizon, where it heats up and produces radiation.
According to the physicists, when a large blackhole captures a smaller object like a medium-sized star the process causes gravitational radiation to be emitted in a preferential direction.