THE TRANSFORMATIVE YOUNG PULSAR PSR J1846-0258 IN SNR KES 75

The discovery of magnetarlike activity from the young rotationpowered pulsar(RPP) in the supernova remnant (SNR) Kes 75 offers a unique opportunity to studythe connection between RPPs and magnetars, their birth and early evolution. PSRJ18460258 and its wind nebula also provide a unique window on shockacceleration physics taking place in some of the highest Bfields known innature. We propose a joint NuSTAR/XMMNewton observation of Kes 75 tocharacterize its hard Xray emission in a critical energy band and search for aspectral break near virgul10 keV, to help distinguish PWN from magnetar physics. Fora transitionary object, this may indicate the emergence of a buried, magnetarstrength field responsible for powering the rapid spindown of the pulsar and its unusually energetic PWN. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]