Binary population synthesis models for core-collapse gamma-ray burst progenitors

TL;DR

This study uses binary stellar evolution models to explore how certain massive stars can retain enough angular momentum to produce gamma-ray bursts, identifying key progenitor characteristics and pathways consistent with observations.

Contribution

It introduces a detailed binary population synthesis approach to identify pathways for GRB progenitors, incorporating tidal interactions and angular momentum retention.

Findings

Two pathways for GRB progenitors: accretion-induced spin-up and tidal maintenance of rotation.

Thresholds for supernova types based on hydrogen and helium mass fractions.

Reproduces observed GRB rate evolution and host galaxy metallicity distribution.

Abstract

Long-duration gamma-ray bursts (GRBs) are understood to be the final fate for a subset of massive, stripped envelope, rapidly rotating stars. Beyond this, our knowledge of the progenitor systems is limited. Using the BPASS (Binary Population and Spectral Synthesis) stellar evolution models, we investigate the possibility that some massive stars in binaries can maintain the angular momentum required for jet production, while still loosing their outer envelope through winds or binary interactions. We find that a total hydrogen mass of less than 0.0005 Msun and a helium ejecta mass fraction of less than 0.20 provide the best thresholds for the supernova type II/Ibc and Ib/Ic divisions respectively. Tidal interactions in binaries are accounted for by applying a tidal algorithm to post-process the stellar evolution models output by BPASS. We show that the observed volumetric gamma-ray burst rate evolution can be recreated using two distinct pathways and plausible distributions for burst parameters. In the first pathway, stars are spun up by mass accretion into a quasi-homogeneous state. In the second, tides maintain rotation where otherwise the star would spin down. Both lead to type Ic supernova progenitors, and a metallicity distribution consistent with the GRB host galaxy population. The inferred core angular momentum threshold for jet production is consistent with theoretical requirements for collapsars, given the assumptions made in our model. We can therefore reproduce several aspects of core collapse supernova/GRB observation and theory simultaneously. We discuss the predicted observable properties of GRB progenitors and their surviving companions.