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

Abstract

THESEUS, one of the two space mission concepts being studied by ESA as\ncandidates for next M5 mission within its Comsic Vision programme, aims at\nfully exploiting Gamma-Ray Bursts (GRB) to solve key questions about the early\nUniverse, as well as becoming a cornerstone of multi-messenger and time-domain\nastrophysics. By investigating the first billion years of the Universe through\nhigh-redshift GRBs, THESEUS will shed light on the main open issues in modern\ncosmology, such as the population of primordial low mass and luminosity\ngalaxies, sources and evolution of cosmic re-ionization, SFR and metallicity\nevolution up to the "cosmic dawn" and across Pop-III stars. At the same time,\nthe mission will provide a substantial advancement of multi-messenger and\ntime-domain astrophysics by enabling the identification, accurate localisation\nand study of electromagnetic counterparts to sources of gravitational waves and\nneutrinos, which will be routinely detected in the late '20s and early '30s by\nthe second and third generation Gravitational Wave (GW) interferometers and\nfuture neutrino detectors, as well as of all kinds of GRBs and most classes of\nother X/gamma-ray transient sources. In all these cases, THESEUS will provide\ngreat synergies with future large observing facilities in the multi-messenger\ndomain. A Guest Observer programme, comprising Target of Opportunity (ToO)\nobservations, will expand the science return of the mission, to include, e.g.,\nsolar system minor bodies, exoplanets, and AGN.\n