NSVS 11868841: An active detached eclipsing binary system with a substellar object

Abstract Four-color CCD photometric light curves (LCs) of eclipsing binary (EB) NSVS 11868841 are presented in this paper. These LCs are analyzed by using the 2013 version of the Wilson–Devinney (W–D) code. We found that NSVS 11868841 is a late-type low-mass detached EB with an orbit inclination nearly 90 ° . The LCs are asymmetric, especially in its out-of-eclipse. Based on all available times of the light minimum, we analyzed the variations of the orbital period by using the ( O – C ) method. The O–C curve shows a cycle oscillation with a period of 11.83( ± 0 . 04 ) years and an amplitude of 0.0009 days ( ∼ 1.3 min). This cyclic change detected in NSVS 11868841 could be explained by the light-travel time effect (LTTE) via the presence of a third body. Subsequently, we calculated the mass of this third component as M 3 sin( i 3 )=0.047( ± 0 . 015 ) M ⊙ . If the third body is coplanar with the central system, it may be a brown dwarf. And this discovery will provide important insights on the formation and evolution of brown dwarf companions.