Exoclock project. IV. A homogeneous catalog of 620 updated exoplanet ephemerides

The ExoClock project is an open platform aiming to monitor exoplanets by integrating observations from space- and ground-based telescopes. This study presents an updated catalog of 620 exoplanet ephemerides, integrating 30,000 measurements from ground-based telescopes (the ExoClock network), literature, and space telescopes (Kepler, K2 and TESS). The updated catalog includes 277 planets from TESS which require special observing strategies due to their shallow transits or bright host stars. This study demonstrates that data from larger telescopes, and the employment of new methodologies such as synchronous observations with small telescopes, are capable of monitoring special cases of planets. The new ephemerides show that 45% of the planets required an update while the results show an improvement of 1 order of magnitude in prediction uncertainty. The collective analysis also enabled the identification of new planets showing transit-timing variations, highlighting the importance of extensive observing coverage. Developed in the context of the ESA’s Ariel space mission, with the goal of delivering a catalog with reliable ephemerides to increase the mission efficiency, ExoClock’s scope and service have grown well beyond the remit of Ariel. The ExoClock project has been operating in the framework of open science, and all tools and products are accessible to everyone within academia and beyond, to support efficient scheduling of future exoplanet observations, especially from larger telescopes where the pressure for time allocation efficiency is higher (Ariel, JWST, VLT, ELT, Subaru etc.). The inclusion of diverse audiences in the process and the collaborative mode not only foster democratization of science but also enhance the quality of the results.