GeV emission from a compact binary merger

Understand

An energetic $\rm \gamma$-ray burst (GRB), GRB 211211A, was observed on 2021 December 11 by the Neil Gehrels Swift Observatory.

• Despite its long duration, typically associated with bursts produced by the collapse of massive stars, the discovery of an optical-infrared kilonova and a quasi-periodic oscillation during a gamma-ray precursor points to a compact object binary merger origin.
• The complete understanding of this nearby ($\sim$ 1 billion light-years) burst will significantly impact our knowledge of GRB progenitors and the physical processes that lead to electromagnetic emission in compact binary mergers.
• Here, we report the discovery of a significant ($\rm >5 \sigma$) transient-like emission in the high-energy $\rm \gamma$-rays (HE; E$>0.1$ GeV) observed by Fermi/LAT starting at $10^3$ s after the burst.