Possible Presence of a Third Body in the Kepler K2 Variable EPIC 202073314

Abstract

Abstract We report the presence of an unseen third-body companion in a low-mass-ratio deep contact binary system Kepler K2 EPIC 202073314 as seen by the presence of the light time effect (LITE) on the O–C diagram. The system is found to be exhibiting an increasing period trend along with a sinusoidal behavior of the O–C residuals owing to the LITE variations. The residuals are modeled initially assuming a circular orbit to obtain a third-body orbital period of ∼9.75 years. We further performed a rigorous analysis by allowing the eccentricity to vary, which led to a third-body orbital period of ∼8.66 years with e 3 = 0.51. We also report the photometric study of this variable. The system is found to have a mass ratio of ∼0.15 with an inclination of ∼77°. Monte-Carlo simulations were performed to verify the consistency of the obtained photometric solution. The system is considered to be in significant geometrical contact as seen by the high fill-out factor of ∼57%. Magnetic inactivity of the system is understood in terms of the absence of O’ Connell effect and lack of fill-in effect in the Hα spectral line. The dynamical state of the system is discussed in terms of the Hut’s stability criteria ( ) as the low-mass and high fill-out factor configuration of the system makes it a promising candidate in the context of stellar mergers. Assuming conservative mass transfer, the system is expected to meet the critical mass ratio of ∼0.07–0.09 in ∼106 years.