The THESEUS space mission: science goals, requirements and mission concept

Abstract THESEUS, one of the two space mission concepts being studied by ESA as candidates for next M5 within its Comsic Vision programme, aims at fully exploiting Gamma-Ray Bursts (GRB) to solve key questions about early Universe, well becoming a cornerstone multi-messenger and time-domain astrophysics. By investigating first billion years Universe through high-redshift GRBs, THESEUS will shed light on main open issues in modern cosmology, such population primordial low mass luminosity galaxies, sources evolution cosmic re-ionization, SFR metallicity up “cosmic dawn” across Pop-III stars. At same time, provide substantial advancement astrophysics enabling identification, accurate localisation study electromagnetic counterparts gravitational waves neutrinos, which be routinely detected late ‘20s ‘30s second third generation Gravitational Wave (GW) interferometers future neutrino detectors, all kinds GRBs most classes other X/gamma-ray transient sources. Under these respects, great synergies with large observing facilities domain. A Guest Observer comprising Target Opportunity (ToO) observations, expand science return mission, include, e.g., solar system minor bodies, exoplanets, AGN.