The Best Brown Dwarf Yet? A Companion to the Hyades Eclipsing Binary V471 Tauri

Abstract

We have carried out an analysis of about 160 eclipse timings spanning over 30 years of the Hyades eclipsing binary V471 Tauri that shows a long-term quasi-sinusoidal modulation of its observed eclipse arrival times. The O C values have been analyzed for the "light-time" effect that arises from the gravitational influence of a tertiary companion. The presence of a third body causes the relative distance of the eclipsing pair to the Earth to change as it orbits the barycenter of the triple system. The result of the analysis of the eclipse times yields a light-time semiamplitude of s, an orbital period of yr, and an eccentricity of 137.2 12.0 P p 30.5 1.6 3. The mass of the tertiary component is M when a total mass e p 0.31 0.04 M sin i 0.0393 0.0038 3 3 3 , of M for V471 Tau is adopted. For orbital inclinations , the mass of the third body would 1.61 0.06 i 35 , 3 be below the stable hydrogen-burning limit of M , and thus it would be a brown dwarf. In the next M ≈ 0.07 , several years (near maximum elongation), it should be feasible to obtain IR images and spectra of V471 Tau C that, when combined with the known mass, age, distance, and [Fe/H], will serve as a benchmark for understanding the physical properties and evolution of brown dwarfs.