  We searched for a short-term X-ray variability of the M87 core and jet from
archival X-ray data with long exposure data taken by the Suzaku, Chandra, and
NuSTAR telescopes. We found the intraday variability for the Suzaku data
obtained in 2006, and for the Chandra core obtained in 2017. The intraday
variability suggested a minute emission region of about the size of
Schwartzshild radius of the M87 supermassive black hole. Suzaku could not
resolve a core and HST-1; however, in 2006, HST-1 was much brighter than the
core, and thus, the variability is likely due to the HST-1. Since the photon
index in 2006 was 2.38, the emission was possibly synchrotron emission from the
local shock region in the HST-1, indicating that the particle acceleration of
TeV electrons occurred far away (~100 pc) from the core. Assuming the fading
time to be equal to the synchrotron cooling time, the magnetic field is
constrained to be B ~1.94 ${\delta}^{1/3}$ mG. Moreover, the photon index of
the core in 2017 was approximately 1.96; thus, the possible emission was from
the radiative inefficiency accretion flow of the core or inverse Compton
scattering in the jet. Intraday time variability prefers the latter
possibility.
