DS Andromedae: A Detached Eclipsing Double-lined Spectroscopic Binary in the Galactic Cluster NGC 752 Publications of the RAO No. 77

The Wilson-Devinney program has been used to analyze well-calibrated photometric and new radial velocity data to determine the properties and distance of DS Andromedae, a 1.01 day period, double-lined, totally eclipsing binary system of early-F spectral type and a likely member of the intermediate-age open cluster NGC 752. The determinations of many of the system elements including the distance are robust against modest changes in model assumptions. Third light is present in all passbands at the 10% level. The weighted means of the best-fitting model yield a distance of 477 4 12 pc, equivalent to (m - M)0 = 8.390 0.018 0.060 mag, and masses of 1.655 0.003 0.030 MSun and 1.087 0.005 0.040 MSun, radii of 2.086 0.003 0.013 and 1.255 0.005 0.012 RSun, and effective temperatures 7056 21 140 RSun and 5971 33 130 K, for components 1 and 2, respectively, where the formal internal uncertainties are followed by conservatively estimated systematic errors. Possible but less satisfactory semidetached models produce more parameter variations and larger mean residuals. The primary star is seen to be at or very close to the main-sequence turnoff at an age of 1.55 0.05 Gyr but appears to be too small for its mass, whereas the secondary appears to be too luminous for its temperature and too large for its mass compared to models of single stars.