Evaporation of a Kerr-black-bounce by emission of scalar particles

Abstract

We study a regular rotating black hole evaporating under the Hawking emission of a single scalar field. The black hole is described by the Kerr-black-bounce metric with a nearly extremal regularizing parameter $\ell=0.99r_+$. We compare the results with a Kerr black hole evaporating under the same conditions. Firstly, we compute the gray-body factors and show that the Kerr-black-bounce evolves towards a non-Schwartzchild-like asymptotic state with $a_* \sim 0.47$, differently from a Kerr black hole whose asymptotic spin would be $a_* \sim 0.555$. We show that this result depends on the combined contributions of the differences in the gray-body factors and the surface gravity affected by the regularizing parameter. We also discuss how the surface gravity affects the temperature and the primary emissivity and decreases those quantities with respect to the Kerr black hole. Consequently, the regular black hole has a longer lifetime. Finally, we briefly comment on the possibility of investigating the beyond-the-horizon structure of a black hole exploiting its Hawking emission.