Tentative Evidence for Transit-timing Variations of WASP-161b

We report on the detection of transit-timing variations (TTV) of WASP-161b by using the combination of Transiting Exoplanet Survey Satellite (TESS) data and archival data. The midpoint of the transits in TESS data are offset by ~67 minutes in 2019 January, and ~203 minutes in 2021 January, based on the ephemeris published in previous work. We are able to reproduce the transit timings from the archival light curve (SSO-Europa; 2018 January) and find that the timing is consistent with the published ephemeris under a constant period assumption. Conversely, we find that the transit midpoint of the SSO-Europa light curve indicates a 6.97 minutes variation at 4.63σ compared to the prediction obtained from TESS timings, and a constant orbit period assumption. The TTVs could be modeled with a quadratic function, yielding a constant period change. The period derivative $\dot{P}$ is -1.16 × 10^-7 ± 2.25 × 10^-8 days per day (or -3.65 s yr^-1), using timings obtained from SSO-Europa and TESS light curves. Different scenarios, including a decaying period and apsidal precession, can potentially explain these TTVs but they both introduce certain inconsistencies.