  Two Chandra observations of the R Aqr symbiotic binary system taken 3.3 years
apart show dramatic changes in the X-ray morphology and spectral
characteristics in the inner 500 AU of this system. The morphology of the soft
X-ray emission has evolved from a nearly circular region centered on the binary
system to an hourglass shape that indicates the formation of a new southwest
jet. Synchrotron radiation from the new jet in contemporaneous VLA radio
spectra implies the physical conditions in the early stages of jet development
are different from those in the more extended outer thermal jets known to exist
for decades in this system. The central binary source has two X-ray spectral
components in each of the two epochs, a soft component and a highly absorbed
hard component characterized by T ~ 10^8 K if fit with a thermal plasma model.
The spectrum hardened considerably between 2000.7 and 2004.0, primarily due to
increased flux above 5 keV, suggesting a change in the accretion activity of
the white dwarf on a timescale of a few years or less. Point-source Fe K
emission is detected at the position of the central binary system in both
observations. While the earlier observation shows evidence of only a single
emission peak near Fe K alpha at 6.4 keV, the later observation shows a more
complex emission structure between 6 and 7 keV. Finally, we have discovered a
modulation in the hard X-ray flux with a period of 1734 s at a 95% confidence
level in the 2004 observation only. The modulation potentially arises from
standing shocks in an accretion column and we have explored the possibility
that the white dwarf in R Aqr is analogous to the magnetic white dwarfs in
Intermediate Polar.
