Possible companions in low-mass eclipsing binaries: V380 Dra, BX Tri, and V642 Vir

We present the new results of our long-term observational project to analyze the orbital period variations of low-mass eclipsing binaries. More then 200 new precise mid-eclipse times recorded with a CCD were obtained for three eclipsing binaries with short orbital periods: V380 Dra (P = 0. 49), BX Tri (0. 19), and V642 Vir (0. 52). Observed-minus-calculated diagrams of the stars were analyzed using all reliable timings, and new parameters of the light-time effect were obtained. We derived for the first time the short orbital periods of possible third bodies of 10–20 years for these objects. We calculated that the minimum masses of the third component are close to 0.2 M , which corresponds to the mass of M4 – M5 red dwarfs. The multiplicity of these systems also plays an important role in the precise determination of their physical parameters.