A novel paradigm for short gamma-ray bursts with extended X-ray emission

TL;DR

This paper introduces a new model explaining the sustained X-ray afterglows in some short gamma-ray bursts, linking merger dynamics with prolonged emission and unifying features of short and long GRBs.

Contribution

It presents a novel paradigm that accounts for long-term X-ray emission in SGRBs through merger products and outflow interactions, supported by simulations.

Findings

Explains sustained X-ray afterglows in SGRBs.

Shows how X-ray emission precedes gamma-ray emission.

Unifies phenomenology of short and long GRBs.

Abstract

The merger of a binary of neutron stars provides natural explanations for many of the features of short gamma-ray bursts (SGRBs), such as the generation of a hot torus orbiting a rapidly rotating black hole, which can then build a magnetic jet and provide the energy reservoir to launch a relativistic outflow. Yet, this scenario has problems explaining the recently discovered long-term and sustained X-ray emission associated with the afterglows of a subclass of SGRBs. We propose a new model that explains how an X-ray afterglow can be sustained by the product of the merger and how the X-ray emission is produced before the corresponding emission in the gamma-band, although it is observed to follow it. Overall, our paradigm combines in a novel manner a number of well-established features of the emission in SGRBs and results from simulations. Because it involves the propagation of an ultra-relativistic outflow and its interaction with a confining medium, the paradigm also highlights a unifying phenomenology between short and long GRBs.