Study on the variation of orbital period, quasi-periodic oscillations and negative superhumps in V729 Sgr

Based on K2 and our observations of V729 Sgr, the study of the variation of orbital period, quasi-periodic oscillations (QPOs) and negative superhumps are presented. Using all available mid-eclipse times during quiescence, we find that V729 Sgr has a cyclic variation of the orbital period, with periods and amplitudes of ∼9.64 years and ∼442.37 s, respectively. Based on the interpret of light travel-time effect, the mass of third body is derived as M3sini′=0.24(±0.016)M⊙. When the third body is coplanar with the central body system, the third body may be a low-mass star. Using the Weighted Wavelet Z-transform (WWZ) method, we find for the first time that V729 Sgr has QPOs with the period of ∼1030–3370 s. Using WWZ method, we find that V729 Sgr also has negative superhumps in the first quiescence, indicating that the negative superhumps may be permanent in the quiescence of V729 Sgr.