The THESEUS space mission concept: science case, design and expected performances

TL;DR

THESEUS is a proposed space mission designed to detect and analyze gamma-ray bursts and X-ray transients, enabling breakthroughs in understanding the early universe, cosmic re-ionization, and multi-messenger astrophysics through advanced instruments and rapid follow-up capabilities.

Contribution

It introduces a comprehensive mission concept combining wide-field gamma-ray and X-ray detection with onboard IR follow-up, advancing multi-messenger and time-domain astrophysics research.

Findings

Potential to study star formation up to redshift ~10

Capability to detect electromagnetic counterparts to gravitational waves

Enhanced understanding of re-ionization and early universe phenomena

Abstract

THESEUS is a space mission concept aimed at exploiting Gamma-Ray Bursts for investigating the early Universe and at providing a substantial advancement of 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 field of view (more than 1sr) with 0.5-1 arcmin localization, an energy band extending from several MeV down to 0.3 keV and high sensitivity to transient sources in the soft X-ray domain, as well as on-board prompt (few minutes) follow-up with a 0.7 m class IR telescope with both imaging and spectroscopic capabilities. THESEUS will be perfectly suited for addressing the main open issues in cosmology such as, e.g., star formation rate and metallicity evolution of the inter-stellar and intra-galactic medium up to redshift $\sim$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 provide unprecedented capability to monitor 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 late '20s / early '30s by next generation facilities like aLIGO/ aVirgo, eLISA, KAGRA, and Einstein Telescope. THESEUS will also provide powerful synergies with the next generation of multi-wavelength observatories (e.g., LSST, ELT, SKA, CTA, ATHENA).