Entropy of an 'arbitrarily accelerating' Kinnersley black hole

In the case of the brick-wall model for a static black hole, the Bekenstein-Hawking entropy is the contributions of the fields in the vicinity of the horizon, which sometimes is called as the improved brick-wall model, or the thin film model. According to this idea, the entropy of the 'arbitrarily accelerating' Kinnersley black hole is computed by using the assumption of local equilibrium near the horizon. First, by the generalized tortoise coordinate transformation we get the Hawking radiation temperature and spectrum, which indicates the particle has chemical potential originated from the acceleration of the black hole. Second, we obtain the entropy of the hole, which is proportional to its area with the same geometrical cutoff relationship as in the static case and relies on the notion of the local equilibrium crucially that can be met if the evaporation of the hole is negligible and the change of the acceleration is slow