Uppsala participation in Plato

Project title: Uppsala participation in Plato
Main applicant: Ulrike Heiter, Division of Astronomy and Space Physics
Co-applicant: Oleg Kochukhov, Division of Astronomy and Space Physics
Grant amount: SEK 4 375 855 for the period 2024-2026

The Plato mission is to be launced by ESA in 2026, and will detect terrestrial exoplanets from photometric transits. Key scientific goals are to fundamently enhance our understanding of the transformation and the evolution of planetary systems and to identify potentially habitable planets. Achieving these goals requires to determine bulk properties of the detected planets (radius and mass), which depend on the corresponding properties of the host stars. Furthermore, a detailed characterisation of the stellar-exoplanet environment is critical, including the host star radiation field and magnetosphere.

The accurate determination of host star properties will be based on complimentary ground-based observations, and the development of sophisticated analysis methods using state-of-the-art stellar atmosphere models with up-to-date physical ingredients. The Uppsala participation in the Plato Mission Consortium focuses on the coolest stars targeted by Plato, a sample of at least 5000 M dwarves. We are leading the development of the analysis software to determine global properties of M dwarves, including metallicity, chemical abundances, and magnetic field indicators, based on spectroscopic and photometric data. The analysis pipeline will be validated on a set of benchmark stars and delivered to ESA for the characterisation of the M-dwarf sample among the Plato targets.

In another component of this application we will explore the possibility of using constant and regularly variable early-type calibrator stars for monitoring the long-term stability of the Plato photometry. We will compile samples of suitable calibrators in the Plato long-duration observation fields and test relevant light curve processing algorithms using observations of similar stars obtained by the TESS mission.