Connecting the early afterglow to the prompt GRB and the central engine in the striped jet model

TL;DR

This paper tests the striped jet model for GRBs by comparing its predictions with observed spectra, finding it consistent with many bursts and suggesting a neutron star central engine is more likely.

Contribution

It evaluates the striped jet model against observational data, linking jet properties to the nature of the central engine and proposing a broader stripe distribution for better dissipation modeling.

Findings

Model's photospheric emission peak matches observed spectra in most bursts.

Approximately 10% radiative efficiency of the jet predicted by the model.

More bursts are compatible with a neutron star central engine than a black hole.

Abstract

Despite a generally accepted framework for describing the Gamma-Ray Burst (GRB) afterglows, the nature of the compact object at the central engine and the mechanism behind the prompt emission remain debated. The striped jet model is a promising venue to connect the various GRB stages since it gives a robust prediction for the relation of jet bulk acceleration, magnetization and dissipation profile as a function of distance. Here, we use the constraints of the magnetization and bulk Lorentz of the jet flow at the large scales where the jet starts interacting with the ambient gas in a large sample of bursts to (i) test the striped jet model for the GRB flow and (ii) study its predictions for the prompt emission and the constraints on the nature of the central engine. We find that the peak of the photospheric component of the emission predicted by the model is in agreement with the observed prompt emission spectra in the majority of the bursts in our sample, with a radiative efficiency of about 10 per cent. Furthermore, we adopt two different approaches to correlate the peak energies of the bursts with the type of central engine to find that more bursts are compatible with a neutron star central engine compared to a black hole one. Lastly, we conclude that the model favors broader distribution of stripe length-scales which results in a more gradual dissipation profile in comparison to the case where the jet stripes are characterized by a single length-scale.