  PSR J1846-0258 is a radio-quiet rotation-powered pulsar at the center of
Supernova remnant Kes 75. It is the youngest pulsar (~723 year) of all known
pulsars and slows down very predictably since its discovery in 2000. Till June
7, 2006 very stable behavior has been displayed both in the temporal and
spectral domains with pulsed emission detectable by INTEGRAL IBIS ISGRI and
RXTE HEXTE up to ~150 keV. Then, a dramatic brightening was detected of the
pulsar during June 7-12, 2006 Chandra observations of Kes 75. This radiative
event, lasting for ~55 days, was accompanied by a huge timing glitch, reported
on for the first in present work. Moreover, several short magnetar-like bursts
were discovered. In this work not only the time-averaged pre-outburst
X-ray/soft gamma-ray characteristics are discussed in detail, but also the
spectral evolution during the outburst and its relaxation phase are addressed
using RXTE PCA and HEXTE and INTEGRAL IBIS ISGRI data.
