Light curve solutions for bright detached eclipsing binaries in SMC: absolute dimensions and distance indicators

This paper presents a careful and detailed light curve analysis of bright detached eclipsing binaries (DEB) in the Small Magellanic Cloud, discovered by OGLE collaboration, on the basis of recently available difference image analysis (DIA) photometry. The 19 binaries brighter than 16.4 mag in I band and with the depth of primary and secondary eclipse greater than 0.25 mag were investigated. The solutions were obtained by a modified version of the Wilson-Devinney program. The quality of DIA light curves – a good phase coverage and relatively small scatter – is enough to calculate realistic estimates for the third light l3 and the argument of periastron ωo. It was found that solutions of detached, eccentric systems with flat light curve between eclipses usually may suffer from indetermination of l3 in contrast to those of similar systems having some proximity effects. The physical properties of the stars were estimated on the basis of their photometric elements and indices assuming the distance modulus to SMC ∼ 18.9 and consistency between an empirical mass-luminosity relation and the flux scaling. The method was tested on three LMC stars of known absolute dimensions and a good agreement was found for m−M ∼ 18.5. Such an approach may give fast and accurate estimates of absolute dimensions for large and homogeneous samples of eclipsing binaries in the Magellanic Clouds and other close galaxies. Moreover, this method allows also for independent estimation of E(B − V ) in the direction to a particular binary. The subset of six bright DEB’s worth future intensive investigations as likely distance indicators to SMC, was chosen. They are SC3 139376, SC4 53898, SC5 129441, SC6 67221, SC6 215965 and SC9 175336.