ASAS Census of Twins

Abstract: Twin binaries were identified among the eclipsing binaries with $\delta$>--30$^\circ$ listed in the ASAS catalog. In addition to the known twin binaries in the literature, 68 new systems have been identified, photometric and spectroscopic observations were done. Color, spectral type, temperature, ratio of radii and masses of the components have been derived and presented. Including 12 twin binary systems that exist in both ASAS and the catalogue of absolute parameters of detached eclipsing binary stars, a total of 80 twin detached binary systems have been statistically studied. A comparison of the spectral type distribution of the twins with those of detached eclipsing binary stars in the ASAS database showed that the spectral type distribution of twins is similar to that of detached systems. This result has been interpreted as there is no special formation mechanism for twins than for normal detached binaries. As a result of our case study for HD~154010, a twin binary, we presented the precise physical parameters of the system.