PoS - Proceedings of Science
Volume 395 - 37th International Cosmic Ray Conference (ICRC2021) - GAD - Gamma Ray Direct
Study of {^{26}Al}$ in the COSI 2016 Superpressure Balloon Flight
J. Beechert*  on behalf of the COSI collaboration
Full text: pdf
Pre-published on: July 04, 2021
Published on: March 18, 2022
The Compton Spectrometer and Imager (COSI) is a balloon-borne compact Compton telescope designed to survey the $\gamma$-ray sky from 0.2 to 5 MeV. COSI's wide field-of-view (FOV) and excellent energy resolution from high-purity germanium detectors make it uniquely capable of probing this under-explored energy regime. In particular, it can facilitate understanding of stellar nucleosynthesis through studies of diffuse emission from the radioisotope $\mathrm{^{26}Al}$ at 1.809 MeV. In 2016, COSI was launched from Wanaka, New Zealand on a NASA superpressure balloon and flew for 46 days. The flight was a technologic and scientific success, boasting live detection and polarization studies of GRB160530A, spectral analysis of the Crab Nebula and the 511-keV positron annihilation emission at the Galactic Center, and detection of Cygnus X-1. This article details the first maximum-likelihood search for the 1.809 MeV signature of Galactic $\mathrm{^{26}Al}$ in the 2016 data. The analysis reveals a promising excess around the expected energies of an $\mathrm{^{26}Al}$ signature with 3.7$\sigma$ significance and a measured flux of (17.0 $\pm$ 4.9) $\times$ 10$^{-4}$ ph cm$^{-2}$ s$^{-1}$. Further exploration is currently underway to solidify the measurement.
DOI: https://doi.org/10.22323/1.395.0611
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