Gravitational Waves from the Propagation of Long Gamma-Ray Burst jets

TL;DR

This paper presents numerical simulations showing how gravitational wave signals from long gamma-ray burst jets can reveal key jet parameters and progenitor star structure, potentially detectable by future GW observatories.

Contribution

The study introduces a method to extract jet and stellar parameters from GW signals generated by relativistic jets in long GRBs, advancing understanding of jet propagation.

Findings

GW signals have two peaks corresponding to jet duration and breakout time.

GW signal slopes track jet luminosity and progenitor star structure.

Future GW detectors could observe these signals, providing new insights into GRB jets.

Abstract

Gamma-ray bursts (GRBs) are produced during the propagation of ultra-relativistic jets. It is challenging to study the jet close to the central source, due to the high opacity of the medium. In this paper, we present numerical simulations of relativistic jets propagating through a massive, stripped envelope star associated to long GRBs, breaking out of the star and accelerating into the circumstellar medium. We compute the gravitational wave (GW) signal resulting from the propagation of the jet through the star and the circumstellar medium. We show that key parameters of the jet propagation can be directly determined by the GW signal. The signal presents a first peak corresponding to the jet duration and a second peak which corresponds to the break-out time for an observer located close to the jet axis (which in turn depends on the stellar size), or to much larger times (corresponding to the end of the acceleration phase) for off-axis observers. We also show that the slope of the GW signal before and around the first peak tracks the jet luminosity history and the structure of the progenitor star. The amplitude of the GW signal is $h_+D \sim$ hundreds to several thousands cm. Although this signal, for extragalactic sources, is outside the range of detectability of current GW detectors, it can be detected by future instruments as BBO, DECIGO and ALIA. Our results illustrate that future detections of GW associated to GRB jets may represent a revolution in our understanding of this phenomenon.