The possible observations of Trojan-like extrasolar planets stimulate the
deeper understanding of the stability behaviour of the co-orbital resonant
motion. By using Hill's equations and the energy-rate method an analysis of the
stability map of the elliptic restricted three-body problem is performed.
Regions of the μ−e parameter plane are described numerically and related to
the resonant frequencies of librational motion. Stability and instability can
therefore be obtained by analysing the two independent frequency modes
depending on system parameters. The key role of the long period libration in
determining the structure of the stability is demonstrated and also a stability
mechanism is found that is responsible for extended life time of the test
particle in the unstable domain of the stability map.Comment: 7 pages, 8 figures, accepted to MNRA