THESEUS: Transient High Energy Sky and Early Universe Surveyor

THESEUS is a space mission concept that is undergoing a Phase A study by ESA as a candidate M7 mission. The mission aims at exploiting Gamma-Ray Bursts for investigating the early Universe and at providing a substantial advancement of multi-messenger and time-domain astrophysics. The mission will exploit high-redshift GRBs for cosmology and allow the identification and study of the electromagnetic counterparts to sources of gravitational waves, which will be routinely detected in the ’30s by next-generation facilities like aLIGO/aVirgo, LISA, KAGRA, and Einstein Telescope (ET), as well as of most classes of X/gamma-ray transient sources. As such, THESEUS will secure ideal synergies with virtually all electromagnetic facilities of the near future like, e.g., LSST, ELT, TMT, SKA, CTA, ATHENA. These breakthrough scientific objectives will be achieved by an unprecedented combination of X/gamma-ray monitors and an on-board NIR telescope.