Polarimetric prospects of a new hard X-soft gamma-ray space mission for next decades

The measurement of the polarization of the high-energy photons from cosmic sources has now become a key observational parameter for understanding the emission mechanisms and the geometry of the active regions involved. Therefore, a mandatory requirement for new instrumentation in this energy regime will provide high sensitivity for polarimetric measurements associated with spectroscopy and imaging. In this perspective, the Advanced Surveyor of Transient Events and Nuclear Astrophysics (ASTENA) mission, which includes two main instruments: the Wide field monitor (WFM-IS), with a large effective area and a wide energy passband (2 keV - 20 MeV); and the Narrow Field Telescope (NFT), with a broad energy passband (50 - 600 keV) with focusing capabilities based on the use of an advanced Laue lens; will both provide high sensitivity for polarimetric measurements. Furthermore, both instruments will include spectometers with a good 3D spatial resolution allowing to perform 3D Compton polarimetry, increasing the possibilities to optimize the event selection. Herein, we report on the results of a Monte Carlo study devoted to optimize the configuration of both instruments, in particular, the modulation factor (Q), the events detection efficiency (Eff) and the Minimum Detectable Polarization (MDP).