X-ray flares and their relation to the inner engine activity of GRBs

TL;DR

This paper investigates the nature of X-ray flares in GRB afterglows, showing they result from late inner engine activity and their energy decreases over time, with accretion processes providing the energy source.

Contribution

It demonstrates that X-ray flare energy declines as a power-law and discusses potential powering mechanisms, emphasizing late-time accretion as a common energy source.

Findings

Flares are common, appearing in about half of observed GRB afterglows.

The energy of flares decreases over time following a power-law.

Late-time accretion can power flares in both short and long GRBs.

Abstract

Flares overlaid on the smooth power-law decay of Swift X-ray afterglows are rather common, appearing in roughly half the observed light curves. They are a manifestation of the late time activity of the inner engine, since their temporal evolution is too fast to be linked to activity taking place in the external shock blastwave. In this paper we show that the energy emitted in the form of flares decreases with time as a power-law. We discuss several possibilities in which the flares can be powered and the source of the observed variability. We show that late time accretion from a disk can provide the necessary energy input in both classes of short duration and long duration gamma-ray bursts.