tokens: flux ratio . The sum of the model primary and rescaled secondary spectra was then rectified to a unit continuum. We then repeated the CCF and tomography analysis of this model set of spectra in the same way as was done with the observed spectra to derive a relationship between reconstructed secondary CCF peak height and the assumed flux ratio at 1525 Å. Interpolating the observed CCF peak height in this relation led to a monochromatic flux ratio estimate of at 1525 Å. This flux ratio is related to the ratio of stellar radii bywhere is the monochromatic surface flux ratio of the stars and is equal to in the continuum at 1525 Å for the adopted temperatures of the two stars in the TLUSTY models. Using the above relation, the resulting radius ratio is , where the uncertainty includes the range of associated with the error in . Koubský et al. ( 2000 ) estimate that the Be star mass and mean radius of 60 Cyg are and , respectively. If we adopt these values, then the mass, radius, and gravity of the subdwarf are , and , respectively. This estimate of the companion mass places it above the Chandrasekhar limit of , so it is possible that the subdwarf may become a neutron star in the future. If so, then 60 Cyg may be a progenitor of a Be X-ray binary system. The estimated gravity of the subdwarf is higher than the limit in the TLUSTY grid that we used in deriving the best-fit . The relative strengths of the spectral features in the model spectra depend on the ionization balance in the model, so if we had used a higher model, we would probably arrive at a slightly higher estimate of and a somewhat lower value of R 2 . It is remarkable that among the now five known Be+subdwarf systems that 60 Cyg and 59 Cyg are separated by about one degree on the sky. The stars are not known as cluster members, but they may be affiliated with other early-type stars in their vicinity. We formed a list of stars with B spectral classifications from the catalog of Skiff ( 2014 ) that are situated within 2 deg of the midpoint between 59 Cyg and 60 Cyg, and then collected proper motions from the Gaia Collaboration et al. ( 2016 ) and parallaxes from Leeuwen ( 2007 ) for these stars. Table 3 shows those selected with proper motions and parallaxes within of those of 59 Cyg (HD 200120) and 60 Cyg (HD 200310). This collection of six objects may form part of a hitherto unknown co-moving group of equal age stars. If so, then 59 Cyg and 60 Cyg may be at a similar stage of binary evolution because of their common origin and age. Table 3 Co-moving Stars in the Vicinity of 59 Cyg and 60 Cyg Note. The spectral classifications are from the collection by Skiff ( 2014 ), proper motions and are from the Gaia Collaboration et al. ( 2016 ), and parallaxes are from van Leeuwen ( 2007 ). The V magnitude and radial velocity data are from SIMBAD, with the exception of the systemic velocities for 59 Cyg (Peters et al. 2013 ) and 60 Cyg (Koubský et al. 2000 ). We found no evidence of the
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