Compton echoes from nearby Gamma-Ray Bursts

TL;DR

This paper explores the concept of Compton echoes from nearby Gamma-Ray Bursts, which are faint, long-lasting X-ray signals caused by scattered emission, potentially observable in close events and providing insights into burst properties and environments.

Contribution

It introduces the idea of detecting Compton echoes from nearby GRBs, highlighting their potential to reveal details about burst mechanisms and surrounding medium density.

Findings

Compton echoes peak in X-rays and last for hundreds to thousands of years.

Detection is possible for nearby bursts with high X-ray energy output and dense environments.

Compton echoes can help determine jet success and environment structure.

Abstract

The recent discovery of gravitational waves from GW170817, associated with a short Gamma-Ray Burst (GRB) at a distance of $40$Mpc, has demonstrated that short GRBs can occur locally and at a reasonable rate. Furthermore, gravitational waves enable us to detect close by GRBs, even when we are observing at latitudes far from the jet's axis. We consider here Compton echoes, the scattered light from the prompt and afterglow emission. Compton echoes, an as yet undetected counterpart of GRBs, peak in X-rays and maintain a roughly constant flux for hundreds to thousands of years after the burst. Though too faint to be detected in typical cosmological GRBs, a fraction of close by bursts with a sufficiently large energy output in X-rays, and for which the surrounding medium is sufficiently dense, may indeed be observed in this way. The detection of a Compton echo could provide unique insight into the burst properties and the environment's density structure. In particular, it could potentially determine whether or not there was a successful jet that broke through the compact binary merger ejecta. We discuss here the properties and expectations from Compton echoes and suggest methods for detectability.