Monitoramento fotométrico de efemérides de trânsitos de exoplanetas e inferência de idade de estrelas hospedeiras

Abstract

We present a photometric monitoring campaign of exoplanet transits carried out with the 0.6 m B&C telescope at the Pico dos Dias Observatory (OPD), aimed at contributing to the conti- nuous update of transit ephemerides within the international collaborative ExoClock project, which supports the preparation of the ESA’s ARIEL mission. By the time of writing, 39 transit observations have been submitted to ExoClock, ensuring the recurrent maintenance of epheme- rides for several planetary systems and enhancing the mission’s observational planning effici- ency. The light curves were analyzed using a custom Python routine based on the PyLightCurve package, which simultaneously corrects for instrumental and atmospheric trends and fits transit models to the data. Transit parameters were refined through Bayesian inference using the Mar- kov Chain Monte Carlo (MCMC) method, providing robust posterior distributions and realistic uncertainties. In several cases, our fits yielded comparable or superior precision to that obtained through the standard ExoClock pipeline, highlighting the importance of selecting appropriate detrending models. Additionally, we performed age inference for a subset of solar-type host stars using the gyrochronology technique, deriving rotation periods from space-based photo- metry (CoRoT and TESS) and applying the gyro-interp algorithm. The estimated ages showed good agreement with literature values except for systems hosting close-in giant planets, where tidal interactions and angular momentum transfer limit the applicability of gyrochronology. This work highlights the importance of continuous ground-based observations for maintaining ephemerides. It underscores the need to combine multiple approaches in characterizing stel- lar and planetary systems, thereby directly supporting the scientific objectives of the ARIEL mission.