Robustness of particle creation in the formation of a compact object

Abstract Hawking predicted that the formation of a black hole by gravitational collapse causes quantum particle creation and the spectrum of the particles is almost thermal. This phenomenon is called Hawking radiation. Recently, it has been predicted that particle creation may drastically change from Hawking radiation to a strong double burst if the gravitational collapse suddenly stops just before the formation of the event horizon. In contrast with Hawking radiation, the burst may be so strong that it can be of observational interest even for collapsing objects with astrophysical mass scales. However, the burst phenomenon has been predicted through studies of idealized models in which a spherical hollow shell begins to collapse, but stops shrinking and eventually settles down to a static “star”. Therefore, one might guess that it could be particular to the hollow shell model. In this paper, we study particle creation due to the gravitational collapse of a spherical object whose interior is filled with matter. In this model, we obtain similar results to those in the case of the hollow shell model. This implies that the double burst is a robust property of particle creation by the sudden braking of gravitational collapse.