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

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 degrees. 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 (similar to 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-circle dot. 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.