086043

Millisecond pulsars have boosted in number thanks to the detection of high energy GeV emission by Fermi. Those in compact binaries with nondegenerate companions comma the redbacks openParRBclosePar comma challenge the evolutionary link between neutron star low mass X-ray binary and rotation-powered radio pulsars with 3 systems found to transit between the two stages.A new gamma-ray source has been recently identified with the energetic radio pulsar PSRJ1431-4715 in a RB sharing similarities with the 3 transitional pulsars. We propose to study for the first time the X-ray emission arising from an intrabinary shock between the powerful pulsar and companion winds to determine the energy budget and the amount of irradiation of the companion comma a key parameter to understand how RBs undergo transitions.