  On 2008 May 2, Chandra observed the X-ray spectrum of Xi Boo (G8 V+K4 V),
resolving the binary for the first time in X-rays and allowing the coronae of
the two stars to be studied separately. With the contributions of Xi Boo A and
B to the system's total X-ray emission now observationally established (88.5%
and 11.5%, respectively), consideration of mass loss measurements for GK dwarfs
of various activity levels (including one for Xi Boo) leads to the surprising
conclusion that Xi Boo B may dominate the wind from the binary, with Xi Boo A's
wind being very weak despite its active corona. Emission measure distributions
and coronal abundances are computed for both stars and compared with Chandra
measurements of other moderately active stars with G8-K5 spectral types, all of
which exhibit a narrow peak in emission measure near log T=6.6, indicating that
the coronal heating process in these stars has a strong preference for this
temperature. As is the case for the Sun and many other stars, our sample of
stars shows coronal abundance anomalies dependent on the first ionization
potential (FIP) of the element. We see no dependence of the degree of "FIP
effect" on activity, but there is a dependence on spectral type, a correlation
that becomes more convincing when moderately active main sequence stars with a
broader range of spectral types are considered. This clear dependence of
coronal abundances on spectral type weakens if the stellar sample is allowed to
be contaminated by evolved stars, interacting binaries, or extremely active
stars with log L_X>29, explaining why this correlation has not been recognized
in the past.
