Time domain astronomy with the THESEUS satellite

Abstract

THESEUS is a medium size space mission of the European Space Agency, currently under evaluation for a possible launch in 2032. Its main objectives are to investigate the early Universe through the observation of gamma-ray bursts and to study the gravitational waves electromagnetic counterparts and neutrino events. On the other hand, its instruments, which include a wide field of view X-ray (0.3-5 keV) telescope based on lobster-eye focussing optics and a gamma-ray spectrometer with imaging capabilities in the 2-150 keV range, are also ideal for carrying out unprecedented studies in time domain astrophysics. In addition, the presence onboard of a 70 cm near infrared telescope will allow simultaneous multiwavelegth studies. Here we present the THESEUS capabilities for studying the time variability of different classes of sources in parallel to, and without affecting, the gamma-ray bursts hunt.

Characterizing the Advective Hot Flows of Nova-like Cataclysmic Variables in the X-Rays: The Case of BZ Cam and V592 Cas

“…However, the extent and nature of the X-ray flows are not fully justified in accordance with these new models. It has been suggested that the accretion flows in nonmagnetic white dwarf binaries are well explained in the context of radiatively inefficient advective hot flows in the X-ray regime (Balman & Revnivtsev 2012;Balman 2020;Mereghetti et al 2021). This work is an extrapolation and development of our previous works on the two NLs regarding advection-dominated accretion flows in the X-rays (Balman et al 2014;Godon et al 2017).…”

Breakthrough Multi-Messenger Astrophysics with the THESEUS Space Mission

“…From ELT to ATHENA, CTA to Einstein Telescope, the Vera Rubin Observatory to the Roman Space Telescope, the science returns from combining observations with multiple facilities is a classic case of "the whole being much greater than the sum of the parts" [26]. A broad range of other science programmes will be enabled by THESEUS, including using observations of GRB emission as laboratories of ultra-relativistic matter and, e.g., for testing Lorentz invariance [5], as well as gathering statistics on large populations of other high-energy sources and transients [27]. Thus, THESEUS data will be of interest to a very wide user community, also through its open guest-observer programme.…”

“…At the same time, the goals for multi-messenger astrophysics and time domain astronomy require:(i) a substantial advance in the detection and localization, over a large (>2 sr) FoV of short GRBs as electromagnetic counterparts of GW signals coming from BNS, and possibly NS-BH mergers; (ii) monitoring the high-energy sky with an unprecedented combination of sensitivity, location accuracy and field of view in the soft X-rays; iii) imaging up to the hard X-rays and spectroscopy/timing of the soft gamma-rays [27,29,30].…”

The X/Gamma-ray Imaging Spectrometer (XGIS) for THESEUS and other mission opportunities

“…The Transient High-Energy Sky and Early Universe Surveyor (THESEUS) mission concept [1][2][3] aims at fully exploiting Gamma-Ray Bursts (GRB) for early Universe and multi-messenger astrophysics, as well as providing a substantial advance in time-domain astronomy through detection, accurate location, multi-wavelength (0.3 keV -10 MeV plus near IR) characterization, and redshift measurement, of many classes of high-energy transients [4][5][6][7][8][9] . Developed by a large international collaboration, in 2018 THESEUS was selected by ESA for a three years Phase 0/A study as one of the three candidates for the M5 medium-class space mission opportunity for a launch in ~2032 3 .…”

“…This breakthrough performance can be achieved by overcoming the current limitations through an extension of the GRB monitoring passband to the soft X-rays with an increase of at least one order of magnitude in sensitivity with respect to previously flown wide-field X-ray monitors, as well as a substantial improvement of the efficiency of counterpart detection, spectroscopy and redshift measurement through prompt on-board NIR follow-up observations. At the same time, the objectives on multi-messenger astrophysics [5][6] and, more generally, time domain astronomy [7][8][9] and synergies with future very large facilities [10][11] , require: a) a substantial advancement in the detection and localization, over a large (> 2 sr) Field-of-View (FoV) of short GRBs as electromagnetic counterparts of GW signals coming from NS-NS, and possibly NS-BH) mergers; b) monitoring the high-energy sky with an unprecedented combination of sensitivity, location accuracy and field of view in the soft X-rays; c) imaging up to the hard X-rays and spectroscopy / timing to the soft gamma-rays.…”