  We report on deep Chandra observations of the nearby broad-line radio galaxy
Pictor A, which we combine with new Australia Telescope Compact Array (ATCA)
observations. The new X-ray data have a factor 4 more exposure than
observations previously presented and span a 15-year time baseline, allowing a
detailed study of the spatial, temporal and spectral properties of the AGN,
jet, hotspot and lobes. We present evidence for further time variation of the
jet, though the flare that we reported in previous work remains the most
significantly detected time-varying feature. We also confirm previous tentative
evidence for a faint counterjet. Based on the radio through X-ray spectrum of
the jet and its detailed spatial structure, and on the properties of the
counterjet, we argue that inverse-Compton models can be conclusively rejected,
and propose that the X-ray emission from the jet is synchrotron emission from
particles accelerated in the boundary layer of a relativistic jet. For the
first time, we find evidence that the bright western hotspot is also
time-varying in X-rays, and we connect this to the small-scale structure in the
hotspot seen in high-resolution radio observations. The new data allow us to
confirm that the spectrum of the lobes is in good agreement with the
predictions of an inverse-Compton model and we show that the data favour models
in which the filaments seen in the radio images are predominantly the result of
spatial variation of magnetic fields in the presence of a relatively uniform
electron distribution.
