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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 ofthe two stars to be studied separately. With the contributions of Xi Boo A andB to the system's total X-ray emission now observationally established (88.5%and 11.5%, respectively), consideration of mass loss measurements for GK dwarfsof various activity levels (including one for Xi Boo) leads to the surprisingconclusion that Xi Boo B may dominate the wind from the binary, with Xi Boo A'swind being very weak despite its active corona. Emission measure distributionsand coronal abundances are computed for both stars and compared with Chandrameasurements of other moderately active stars with G8-K5 spectral types, all ofwhich exhibit a narrow peak in emission measure near log T=6.6, indicating thatthe coronal heating process in these stars has a strong preference for thistemperature. As is the case for the Sun and many other stars, our sample ofstars shows coronal abundance anomalies dependent on the first ionizationpotential (FIP) of the element. We see no dependence of the degree of "FIPeffect" on activity, but there is a dependence on spectral type, a correlationthat becomes more convincing when moderately active main sequence stars with abroader range of spectral types are considered. This clear dependence ofcoronal abundances on spectral type weakens if the stellar sample is allowed tobe contaminated by evolved stars, interacting binaries, or extremely activestars with log L_X>29, explaining why this correlation has not been recognizedin the past.

Resolving the Xi Boo Binary with Chandra, and Revealing the Spectral Type Dependence of the Coronal "FIP Effect"