We present the results of time-resolved spectroscopy of 13 O-type stars in the Cas OB6 stellar association .
We conducted a survey for radial velocity variability in search of binary systems , which are expected to be plentiful in young OB associations .
Here we report the discovery of two new single-lined binaries , and we present new orbital elements for three double-lined binaries ( including one in the multiple star system HD 17505 ) .
One of the double-lined systems is the eclipsing binary system DN Cas , and we present a preliminary light curve analysis that yields the system inclination , masses , and radii .
We compare the spectra of the single stars and the individual components of the binary stars with model synthetic spectra to estimate the stellar effective temperatures , gravities , and projected rotational velocities .
We also make fits of the spectral energy distributions to derive E ( B - V ) , R = A _ { V } / E ( B - V ) , and angular diameter .
A distance of 1.9 kpc yields radii that are consistent with evolutionary models .
We find that 7 of 14 systems with spectroscopic data are probable binaries , consistent with the high binary frequency found for other massive stars in clusters and associations .