Measurement of Galactic $^{26}$Al with the Compton Spectrometer and Imager

Understand

The Compton Spectrometer and Imager (COSI) is a balloon-borne compact Compton telescope designed to survey the 0.2-5 MeV sky.

• COSI's energy resolution of $\sim$0.2% at 1.8 MeV, single-photon reconstruction, and wide field of view make it capable of studying astrophysical nuclear lines, particularly the 1809 keV $\gamma$-ray line from decaying Galactic $^{26}$Al.
• Most $^{26}$Al originates in massive stars and core-collapse supernova nucleosynthesis, but the path from stellar evolution models to Galaxy-wide emission remains unconstrained.
• In 2016, COSI had a successful 46-day flight on a NASA superpressure balloon.