The temperature of an object if it is re-radiating all the thermal energy that has been added to it; if an object is not a blackbody radiator, it will not re-radiate all the excess heat and the leftover will go toward increasing its temperature.
A black body is an idealized physical body that absorbs all incident electromagnetic radiation, regardless of frequency or angle of incidence.
A black body in thermal equilibrium (that is, at a constant temperature) emits electromagnetic radiation called black-body radiation. The radiation is emitted according to Planck's law, meaning that it has a spectrum that is determined by the temperature alone (see figure at right), not by the body's shape or composition.
A black body in thermal equilibrium has two notable properties:
1. It is an ideal emitter: it emits as much or more energy at every frequency than any other body at the same temperature.
2. It is a diffuse emitter: the energy is radiated isotropically, independent of direction.
Source: wikipedia, NASA