  We study the quantum particle creation in a toy model of spherically
symmetric gravitational collapse whose final product is not a black hole but a
gravastar. Precedent studies revealed that even in the case of the
gravitational collapse to form a horizonless ultra-compact object, thermal
radiation named transient Hawking radiation is generated at the late stage of
the gravitational collapse, and a sudden stop of collapsing motion to form a
horizonless ultra-compact object causes one or two bursts of quantum particle
creation. The very different behavior of the model studied in this paper from
the precedent ones is quantum radiation with a thermal spectrum from the
gravastar between two bursts. The temperature of the radiation is not the same
as the Hawking one determined by the gravitational mass of the system but the
Gibbons-Hawking one of the de Sitter core inside the gravastar.
