Speaker
Description
Observations in the MeV gamma-ray band provide enormous potential for obtaining fundamental results on topics ranging from nucleosynthesis via studies of nuclear emission lines to multimessenger astrophysics (MMA) through detections of gamma-ray bursts (GRBs) and other transients. Due to the challenges of operating in the MeV band (~0.1-100 MeV), it is one of the least explored regions of the electromagnetic spectrum, leaving a large potential for discovery. In order to take advantage of this scientific opportunity, there is significant activity on space missions that operate in this energy range. Coming up soon is the Compton Spectrometer and Imager (COSI), which is a NASA Small Explorer (SMEX) mission with a planned launch into low-Earth orbit in 2027. Using the Compton technique, COSI will survey the entire sky at 0.2-5 MeV. COSI provides imaging, spectroscopy, and polarimetry of astrophysical sources, and its germanium detectors provide excellent energy resolution for emission line measurements, including the positron annihilation line at 511 keV and nuclear lines. However, COSI only covers part of the "MeV gap," and concepts for covering higher energies are being developed. In this talk, I will give an update on COSI and describe the status of closing the MeV gap.
