Hawking Radiation from the Horowitz--Strominger Black Hole

When a black hole radiates particles, it losses energy and shrinks, the horizon contracts from its original radius to a new smaller radius. This leads to the separation between the initial and final radii, which sets the barrier for the particles to tunnel. We develop the work of Parikh Phys. Rev. Lett. 85(2000)5042; Gen. Rel. Grav. 36,(2004)2419 to a Horowitz--Strominger black hole, i.e. applying the Wentzel--Kramers--Brillouin approximation and semi-classical method to calculate the rate of the Hawking radiation. The result agrees with Γ ～ e^-2ImI=e^ΔS_BH. It is also proven that the energy spectrum deviates from exact thermality.