The Compton Spectrometer and Imager

TL;DR

The Compton Spectrometer and Imager (COSI) is a proposed Small Explorer mission that aims to explore the under-studied MeV gamma-ray band with high sensitivity and resolution, enabling new astrophysical insights.

Contribution

This paper introduces the COSI mission concept, detailing its design, capabilities, and potential scientific impact in gamma-ray astronomy.

Findings

Enhanced sensitivity in the MeV gamma-ray band.

High-resolution spectroscopy of gamma-ray sources.

Ability to measure polarization and localize multimessenger events.

Abstract

In this Astro2020 APC White Paper, we describe a Small Explorer (SMEX) mission concept called the Compton Spectrometer and Imager. COSI is a Compton telescope that covers the bandpass often referred to as the "MeV Gap" because it is the least explored region of the whole electromagnetic spectrum. COSI provides a significant improvement in sensitivity along with high-resolution spectroscopy, enabling studies of 511 keV electron-positron annihilation emission and measurements of several radioactive elements that trace the Galactic history of supernovae. COSI also measures polarization of gamma-ray bursts (GRBs), accreting black holes, and pulsars as well as detecting and localizing multimessenger sources. In the following, we describe the COSI science, the instrument, and its capabilities. We highlight many Astro2020 science WPs that describe the COSI science in depth.