The Universe in the MeV gamma-ray range is characterized by the most
violent explosions, such as mergers, and supernovae, as well as the
most powerful and dynamic sources such as pulsars, and black holes.
The next generation of gamma-ray telescopes will be tasked with
unraveling the life cycle of the elements by observing the
de-excitation of newly generated nuclei from supernovae and mergers,
gaining insight into the evolution and acceleration mechanisms in
jets of, e.g., blazars, contributing to multi-messenger astrophysics
by studying astrophysical events that produce gravitational waves and
neutrinos, better understanding the physics in the most extreme
environments such as neutron stars and near black holes, searching
for signatures of dark matter in the MeV band, solving mysteries such
as the Fermi bubbles and the origin of the Galactic positrons, and
many more. These discoveries will be enabled by the groundbreaking
new capabilities of the next generation of MeV gamma-ray telescopes.
COSI, the Compton Spectrometer and Imager, is a 0.2-5 MeV Compton
telescope capable of imaging, spectroscopy, and polarimetry of
astrophysical sources. Such capabilities are made possible by COSI's
germanium cross-strip detectors, which provide high efficiency, high
resolution spectroscopy and precise 3D positioning of photon
interactions. COSI is currently in a competitive Phase A concept
study to consider COSI as a Small Explorer (SMEX) satellite mission.
As a proof-of-concept of this new generation of telescopes, COSI had
a successful 42-day stratospheric balloon flight in 2016, and was
able to observe the 511-keV emission near the Galactic center region
as well as several other astrophysical sources such as Crab, Cen-A,
and Cyg X-1.
The All-sky Medium-Energy Gamma-ray Observatory Explorer (AMEGO-X) is
an envisioned combined Compton-scattering and pair-creation telescope
operating in the 200 keV to 20 GeV energy range. It will consist of
an electron tracker made of Silicon detectors and a CsI calorimeter.
In the Compton regime it will enable Compton recoil-electron tracking
and thus enable unprecedented background reductions.
GECCO, the Galactic Explorer with Coded aperture mask Compton
telescope, is a mission concept which will operate in the 100 keV to
10 MeV range, and will combine the background reduction and
sensitivity of a Compton telescope with the angular resolution of a coded mask.
In the presentation, we will discuss and compare the science goals,
designs, and current status of these and a few more future MeV
gamma-ray telescope projects, and present the latest results of the
analysis of the 2016 COSI balloon flight.