A Tale of Two Jets: Double Relativistic Outflows from Close Binary GRB Progenitors

TL;DR

This paper models double relativistic jets from close binary GRB progenitors, predicting diverse observational signatures depending on jet alignment and delay, with implications for multi-messenger astronomy.

Contribution

It introduces a comprehensive model for double-jet systems from binary GRB progenitors, analyzing their dynamics and observational signatures.

Findings

Aligned jets produce multiple gamma-ray triggers with spectral evolution.

Misaligned jets can cause off-axis rebrightening and X-ray transients.

Observational features match some existing GRB data.

Abstract

Gravitational wave astronomy has revealed that close binaries with compact companions are widespread. Long GRBs (LGRBs) from massive star collapse face persistent challenges in achieving the rapid core rotation required by the collapsar model. Binary interaction via tidal spin-up offers a natural solution; recent population synthesis studies suggest a substantial fraction of LGRBs may originate from close binaries with a compact companion. In this scenario, supernova ejecta from the primary can be accreted by the companion, potentially launching a second relativistic jet after a delay set by the binary separation. We develop a comprehensive model for these double-jet systems, analyzing the dynamics of the second jet and its interaction with the first. The resulting observational signatures depend critically on the Lorentz factor ratio, the alignment angle, and the time delay. For aligned jets, two regimes arise: a fast second jet producing multiple gamma-ray triggers with distinct spectral/polarization evolution, and a slow second jet where its emission appears as an X-ray flare followed by an afterglow plateau from energy injection. For misaligned jets, the observed signal ranges from normal GRBs with late-time radio structures to fast X-ray transients followed by off-axis rebrightening. These features have observational parallels in existing GRB data. High-resolution radio interferometry with SKA, time-resolved polarimetry with eXTP, and multi-wavelength surveys with Einstein Probe and SVOM will test these predictions, providing constraints on the evolution of close massive binaries as progenitors of GRBs and gravitational wave sources.