GRB afterglows with energy injections in AGN accretion disks

TL;DR

This paper investigates how energy injections from reactivated GRB central engines in AGN disks influence the dynamics and observable afterglows, revealing that injections enable shock breakout and significantly boost afterglow brightness.

Contribution

It introduces a detailed model of energy injections in GRBs within AGN disks, highlighting their effects on shock breakout and afterglow flux enhancement.

Findings

Energy injections enable relativistic shock breakout from AGN disk photosphere.

Energy injections significantly increase GRB afterglow peak flux.

RHDM is largely unaffected by energy injections.

Abstract

Active galactic nucleus (AGN) disks are widely considered potential hosts for various high-energy transients, including gamma-ray bursts (GRBs). The reactivation of GRB central engines can provide additional energy to shocks formed during the interaction of the initially ejected GRB jets with the circumburst material, commonly referred to as energy injections. In this paper, we study GRBs occurring in AGN disks within the context of energy injections. We adopt the standard external forward shock (EFS) model and consider both short- and long-duration GRB scenarios. Light curves for two types of radiation, namely the radiation from the heated disk material (RHDM) and GRB afterglows, are computed. We find that the energy injection facilitates the EFS to break out from the photosphere of the low-density AGN disk at relativistic velocity. Moreover, the energy injection almost does not affect the RHDM but significantly enhances the peak flux of the GRB afterglows.