How to tell a gravastar from a black hole (also when it is rotating...)

Rotating gravastarsIn a recent work (Cardoso et al, 2007), a generalization of the originalstatic, spherically symmetric gravastar model was considered, in orderto describe rotating gravastars.A slow rotation approximation was used to describe the axiallysymmetric spacetime of a rotating gravastar. It was argued thatgravastars might be unstable due to the ergoregion instability.The preliminary results obtained by Cardoso et al indicate that thetime scale of the instability could be very short when compared tothe Hubble time. Further investigation is still needed...