Breakthrough Multi-Messenger Astrophysics with the THESEUS Space Mission

Abstract

The mission concept THESEUS (Transient High Energy Sky and Early Universe Surveyor) aims at exploiting Gamma-Ray Bursts (GRB) to explore the early Universe, as well as becoming a cornerstone of multi-messenger and time-domain astrophysics. To achieve these goals, a key feature is the capability to survey the soft X-ray transient sky and to detect the faint and soft GRB population so far poorly explored. Among the expected transients there will be high-redshift GRBs, nearby low-luminosity, X-ray Flashes and short GRBs. Our understanding of the physics governing the GRB prompt emission will benefit from the 0.3 keV–10 MeV simultaneous observations for an unprecedented large number of hundreds of events per year. In particular the mission will provide the identification, accurate sky localisation and characterization of electromagnetic counterparts to sources of gravitational wave and neutrino sources, which will be routinely detected during the 2030s by the upgraded second generation and third generation Gravitational Wave (GW) interferometers and next generation neutrino detectors.

Future Perspectives for Gamma-ray Burst Detection from Space

“…Although the possible launch dates of STROBE-X and THESEUS are projected relatively far in the future, their timeline could interestingly match the planned observational runs from the third generation of GW detectors, such as the Einstein Telescope (ET) (see, e.g., [63,64] and the references therein) and the Cosmic Explorer (CE) (see, e.g., [65] and the references therein). The enhanced sensitivity of these instruments would greatly increase the number of possibly detected electromagnetic counterparts of GW sources, reaching up to a few tens per year, as reported, e.g., in the case of THESEUS [66].…”

Multifrequency and multimessenger observations of short GRBs and kilonovae

“…Therefore, only the association with a GRB will permit to localize compact-merger events which may also be followed by a kilonova with enough accuracy. This can be provided by future space-based GRB dedicated missions as for example the proposed THESEUS mission [60,61].…”

THESEUS Science on Time-domain Studies of Compact Object Binaries

“…THESEUS has a goal to advance multi-messenger and time-domain astrophysics with a particular aim to exploit Gamma-Ray Burst events for investigating the early Universe [1][2][3]. THESEUS will work with a unique combination of instruments allowing GRB and X-ray transient detection over a broad field of view (> 1 sr) with 0.5-1 arc min localization, an energy band from several MeV down to 0.3 keV and a 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 [1,4].…”

“…The THESEUS payload includes several instruments to achieve the goals described above (Amati et al 2021). The Soft X-ray Imager (SXI) is a set of two sensitive lobster-eye telescopes observing in 0.3-5 keV band with a total FOV of 31×61 deg 2 and source location accuracy < 2 . The X-Gamma ray Imaging Spectrometer (XGIS,) involves 2 coded-mask X-gamma ray cameras using Silicon drift detectors coupled with CsI crystal scintillator bars observing in 2 keV-10 MeV band and an FOV of 117×77 deg 2 (two cameras) overlapping with the SXI, with <15 GRB location accuracy in the 2-150 keV band.…”