Photospheric emission from long duration gamma-ray bursts powered by variable engines

TL;DR

This study uses numerical simulations to explore how variable engines influence the photospheric emission in long gamma-ray bursts, revealing that engine variability does not significantly alter the burst's position in the luminosity-peak frequency plane.

Contribution

It demonstrates through simulations that different engine luminosity profiles produce similar observational signatures in gamma-ray bursts, challenging previous assumptions about engine variability effects.

Findings

Synthetic light-curves follow the Golenetskii correlation.

Engine luminosity profile has minimal impact on burst position in the luminosity-peak frequency plane.

Different engine models are observationally indistinguishable.

Abstract

We present the results of a set of numerical simulations of long-duration gamma-ray burst jets aimed at studying the effect of a variable engine on the peak frequency of the photospheric emission. Our simulations follow the propagation of the jet inside the progenitor star, its break-out, and the subsequent expansion in the environment out to the photospheric radius. A constant and two step-function models are considered for the engine luminosity. We show that our synthetic light-curves follow a luminosity-peak frequency correlation analogous to the Golenetskii correlation found in long-duration gamma-ray burst observations. Within the parameter space explored, it appears that the central engine luminosity profile does not have a significant effect on the location of a gamma-ray burst in the Luminosity-peak frequency plane, bursts from different central engines being indistinguishable from each other.