2106788

Target RA (J2000): 241.824097 and deg Target Dec (J2000): -22.06020 and deg Gaia GMag: 8.519 Programme ID: CH_PR230004 PI of observing programme: Deeg Title of programme: Determining the internal structure of the young hierarchical triple HD 144548 Abstract: HD 144548 is a young (8-11 Myr) triply eclipsing triple star in the Upper Scorpius OB association that displays complex eclipses from simultaneous occultations of all components (syzygys). This system is unique for the availability of both precise Kepler/K2 eclipse light curves from and radial velocities of all three components. In Alonso et al. (2015) we derived the components’ physical and orbital parameters with high precision indicating significantly inflated stellar sizes albeit the size of the system’s largest component is in tension with established models of young stars. With CHEOPS we intend to reobserve several eclipses towards an actualized determination of the systems parameters. Particularly this should lead to a much improved determination of the system’s osculating orbital parameters due to a coverage that would span 9 years versus the 79 days from K2. Such improved osculating parameters should permit a derivation of the internal mass-distribution of the system’s inner binary through determination of the apsidal constant k_2. Reducing uncertainties on the orbital parameters found by Alonso et al. will also significantly improve the precision of the system’s physical parameters and permit a calibration of pre-main sequence star parameters and of the evolution of their stellar interiors. CHEOPS is uniquely suited to perform the observations of the long complex eclipses with a required (and expected) precision that should rival the original Kepler/K2 data. [truncated! Please see actual data for full text]