Observations and analysis of the contact binary H 235 in the open cluster NGC 752

Physical parameters of close binaries QX Andromedae, RW Comae Berenices, MR Delphini, and BD +07° 3142

“…In comparison with previous studies of QX And by Milone et al (1995) and Qian et al (2007), who used the underestimated mass ratio of q ≈ 0.2 obtained from the radial velocities of Milone et al (1995), our solution yields a significantly more massive secondary (M c, Milone = 0.24 M , M c, Quian = 0.27 M , and M c, this study = 0.45 M ), an overcontact parameter that is between their estimated values ( f Milone = 21%, f Quian = 55%, and f this study = 35%), somewhat larger radii of the components (R c, Milone = 0.68 R , R h, Milone = 1.39 R , and R c, this study = 0.88 R , R h, this study = 1.46 R ), and a lower inclination (i Milone ≈ 58 • , i Quian ≈ 56 • , and i this study ≈ 55 • ). The temperatures, absolute bolometric magnitudes, and the estimated distance of the system agree well between these two studies and our own.…”

“…The light variability of the system was first noted by Johnson (1953), and Twarog (1983) pointed out that QX And was probably a binary based on its location in the color-magnitude diagram. The first photometric and spectroscopic observations of QX And were obtained by Milone et al (1995). They analyzed the light and radial velocity curves simultaneously with the WilsonDevinney code (Wilson & Devinney 1971), and obtained a model of an A-type W UMa system with a contact parameter of f = 0.21 ± 0.11 that fit the observations best.…”

“…The radial velocity data of QX And was derived using cross-correlation functions. Unfortunately, the RV observations of Milone et al (1995) were of rather poor quality, resulting in only marginally useful orbital parameters. The authors obtained four light-curve solutions (the spotless, one-spot, two-spot, and three-spot cases) based on their finding that QX And displayed night-to-night variations in its light curves.…”

“…The authors assumed all spots were located on the hotter component. Milone et al (1995) located a spot on one of the components although they performed their solution under the assumption of a radiative envelope. Noticing the mistake in this approach, Qian et al (2007) find that QX And is a deep overcontact binary system with a high degree of overcontact ( f = 55.9%) and a low mass ratio (q = 0.2327).…”

Application of the Direct Distance Estimation procedure to eclipsing binaries in star clusters

“…We use as starting parameters those obtained in fully convergent solutions (see Schiller & Milone 1987, 1988Milone et al 1995 -for work on HD 27130 in the Hyades, and DS And and Heinemann 235 = QX And in NGC 752). Here we report preliminary results only for the the double-lined eclipsing binary in the Hyades, HD 27130 = van Bueren 22 = V818 Tau.…”