Short-duration gamma-ray bursts from off-axis collapsars

TL;DR

This study uses high-resolution simulations to show that off-axis emissions from long gamma-ray burst progenitors can resemble short-duration GRBs with persistent X-ray emission, aligning with observed properties.

Contribution

It introduces a model where off-axis cocoon emissions from long GRBs can explain short GRBs with persistent emission, supported by simulation and observational consistency.

Findings

Cocoon emissions at wide angles resemble short GRBs with persistent X-ray emission.

Predicted duration, redshift, and afterglow brightness match observed short GRB properties.

Host galaxy and late afterglow observations can test the model.

Abstract

We present 2D high-resolution hydrodynamic simulations of the relativistic outflows of long-duration gamma-ray burst progenitors. We analyze the properties of the outflows at wide off-axis angles, produced by the expansion of the hot cocoon that surrounds the jet inside the progenitor star. We find that the cocoon emission at wide angles may have properties similar to those of the subclass of short-duration gamma-ray bursts with persistent X-ray emission. We compute the predicted duration distribution, redshift distribution, and afterglow brightness and we find that they are all in agreement with the observed properties of short GRBs with persistent emission. We suggest that a SN component, the properties of the host galaxies, and late afterglow observations can be used as a crucial test to verify this model.