FL Lyr: Light curve solutions and orbital period analysis by using tess data

Abstract

The detached binary system FL Lyr, has been controversial based on previous studies; some studies have approved the existence of a third body, and a study with spectroscopic data could not confirm it. Based on new TESS observations, previous results have been recalculated and discussed. We extracted the minimum times from the TESS data and presented a new ephemeris based on the space-based observations by using the MCMC method. Based on the data from Kepler and TESS, the residual O-C diagram shows a sinusoidal period. We estimated the orbital period and the minimum mass of this probable third body to be 10.8 years and 5.6 MJ, respectively. However, due to some reasons mentioned in this study, we cannot confirm the existence of a third body. More photometric and spectroscopic data will be required in the future to analyze the orbital period variation of the FL Lyr binary system for the existence or absence of a third body. Light curve solutions of FL Lyr were done by the PHOEBE python code and the MCMC method. This system did not need to add a star-spot in the light curve solutions, and the system's absolute parameters were also obtained.