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Target RA (J2000): 61.331631 and deg Target Dec (J2000): 20.15710 and deg Gaia GMag: 10.08 Programme ID: CH_PR240005 PI of observing programme: Damasso Title of programme: Escape from the “V1298 Tau e labyrinth”: following the CHEOPS’ thread to confirm the orbital period and large TTVs/TDVs of an infant planet Abstract: The object of the proposal is the star V1298 Tau which hosts a system of four transiting planets. The focus of the science case is the confirmation of the orbital period of planet V1298 Tau e and the determination of its transit timing variations (TTVs) and transit duration variations (TDVs) also using archival photometric data collected by Kepler/K2 in 2015 and by TESS in 2021. Previous observations with CHEOPS allowed to identify P=45.00 days as the actual orbital period of planet e (private communication). This results must be necessarily confirmed with further follow-up aimed at detecting additional transits. The same CHEOPS observations revealed a significant TTV and TDV. Observing new transits with CHEOPS is the only way to measure the average orbital period and the TTVs/TDVs and to inform dynamical simulations in order to characterise the evolution of the planets’ orbits over very short timescale (of the order of a few years). The outstanding results expected from the follow-up with CHEOPS will be of great benefit for a proper modelling of hundreds of radial velocities of V1298 Tau collected so far whose analysis has proved very challenging so far. [truncated! Please see actual data for full text]