Programme by Session

THESEUS is a space mission concept under study for the ESA M5 opportunity. It is aimed at exploiting Gamma-Ray Bursts for investigating the early Universe and providing a substantial advance in multi-messenger and time-domain astrophysics. These goals will be achieved through a unique combination of instruments allowing GRB and X-ray transient detection over a broad FOV (more than 1sr) with 0.5-1 arcmin localization, an energy band extending from several MeV down to 0.3 keV and unprecedented sensitivity in the soft X-ray domain, as well as on-board prompt (few minute) follow-up with a 0.7 m class IR telescope with both imaging and spectroscopic capabilities. THESEUS will be perfectly suited for addressing key open issues in cosmology such as, e.g., star formation rate and metallicity evolution of the inter-stellar and inter-galactic medium up to redshift ∼10, signatures of Pop III stars, sources and physics of re-ionization, and the faint end of the galaxy luminosity function. In addition, it will perform an unprecedented monitoring of the X-ray variable sky, thus detecting, localizing, and identifying the electromagnetic counterparts to sources of gravitational radiation, which may be routinely detected in the early 2030s by next generation gravitational wave detectors. THESEUS will also provide powerful synergies with the new multi-wavelength observatories (e.g., LSST, ELT, SKA, CTA, ATHENA etc.).