Before revision:  To characterize the distribution of the burst durations, we determine the distribution of exit points located on the two-dimensional separatrix \Sigma . In addition, we compute analytically the mean burst and AHP durations using a linearization approximation of the dynamical system .
After revision:  To characterize the distribution of the burst durations, we determine the distribution of exit points located on \Sigma that we compute using WKB and the method of characteristics .