Energy extracted from Hartle-Thorne strange stars

It is discussed how Penrose process can be used in a strange star, described by the Hartle-Thorne metric, to extract its rotational energy. This metric has an ergosphere region that depends only on its angular momentum. It is shown that massive particles with negative energy can exist in this ergosphere, exploring the conditions on the radial distance and on angular momentum for this to occur. It is also calculated the total amount of rotational energy that can be extracted from the strange star, and how these conditions cannot be fulfilled by a star with regular matter.