Long Gamma-Ray Bursts and the Morphology of their Host Galaxies

TL;DR

This paper models the origins of long gamma-ray bursts, linking their occurrence to the core collapse of massive stars in binary systems and explaining their host galaxy types through stellar metallicity effects.

Contribution

It introduces a population synthesis model that explains the distribution of host galaxy morphologies for long gamma-ray bursts based on binary star evolution and metallicity-dependent stellar winds.

Findings

Long gamma-ray bursts originate from core collapse in close binaries.

The host galaxy morphology distribution is explained by metallicity-driven stellar wind effects.

Higher metallicity leads to fewer gamma-ray burst progenitors due to increased stellar wind mass loss.

Abstract

We present the results of population syntheses for binary stars carried out using the ``Scenario Machine'' code with the aim of analyzing events that may result in long gamma-ray bursts. We show that the observed distribution of morphological types of the host galaxies of long gamma-ray bursts can be explained in a model in which long gamma-ray bursts result from the core collapse of massive Wolf-Rayet stars in close binaries. The dependence of the burst rate on galaxy type is associated with an increase in the rate of stellar-wind mass-loss with increasing stellar metallicity. The separation of binary components at the end of their evolution increases with the stellar-wind rate, resulting in a reduction of the number of binaries that produce gamma-bursts.