The Prompt Emission of Gamma-Ray Bursts from the Wind of Newborn Millisecond Magnetars: A Case Study of GRB 160804A

TL;DR

This study models the prompt emission of GRB 160804A as resulting from magnetic dissipation in a newborn magnetar's wind, fitting observed spectra and predicting a new subclass of GRBs called MIGMAD bursts.

Contribution

It introduces a combined emission model involving photospheric and synchrotron radiation from magnetar winds, providing physical parameters and predicting a new GRB subclass.

Findings

The model fits the observed spectrum of GRB 160804A.

Physical parameters of the magnetar are derived.

A new subclass of GRBs, MIGMAD bursts, is predicted.

Abstract

In this paper, we revisit the scenario that an internal gradual magnetic dissipation takes place within the wind from a newborn millisecond magnetar can be responsible for gamma-ray burst production. We show that a combination of two emission components in this model, i.e., the photospheric emission from the wind and the synchrotron radiation within the magnetic reconnection region, can give a reasonable fit to the observed spectrum of the prompt emission phase of GRB 160804A. We obtain the physical parameters through a Monte Carlo procedure and deduce the initial spin period and magnetic field of the central magnetar. Furthermore, the independent afterglow fitting analysis gives a consistent result, adding great credibility to this scenario. In addition, we predict a subclass of GRBs called bursts from such a Magnetar wind Internal Gradual MAgnetic Dissipation (abbreviated as "MIGMAD bursts") that have several distinctive properties.