A Comprehensive Study of Three Early-type Contact Twin Binaries: CT Tau, GU Mon, and V701 Sco

Abstract

Abstract Three eclipsing binaries, CT Tau, GU Mon, and V701 Sco, are early-type contact binaries with infrared excess from circumbinary matter. We present the multi-color photometry for CT Tau and GU Mon, whose spectral types of B1V are identified by the low-precision spectra. Combining these new light curves (LCs) with previously reported LCs and radial velocity curves, we perform a synthesized analysis to estimate/update the stellar absolute parameters of the three systems. Their mass ratios are close to unity (i.e., q ≃ 1), which indicates that the binary system comprising of twin components may be undergoing a slow Case A mass transfer. From the period analysis, the light–time orbit in the (O − C) curve may result from the third condense companion around the binary system although no evidence could be provided by the third light ℓ 3. From the spectral energy distribution for three binaries, the excess infrared (IR) emissions are above the photospheric emissions, which can be seen at the 22.1 μm for CT Tau and GU Mon, and 11.6 μm, 14.5 μm, and 22.1 μm for V701 Sco, respectively. This kind of infrared excess for the early-type star may be attributed to the circumbinary matter by stellar wind.