[Paper Review] Stellar evolution with rotation XIII: Predicted GRB rates at various Z

Raphaël Hirschi, G. Meynet+1 more|ArXiv.org|Jul 14, 2005

Gamma-ray bursts and supernovae39 references101 citations

TL;DR

This paper models rotating massive stars across a range of metallicities to predict gamma-ray burst (GRB) rates, finding that only WO-type Wolf-Rayet stars—formed at low metallicities (Z ≈ Z_SMC) and with masses >50 M⊙—satisfy the three collapsar model criteria (black hole formation, H-envelope loss, sufficient angular momentum). The predicted GRB rates from WO stars align closely with observations, unlike models assuming all WR stars as progenitors.

ABSTRACT

We present the evolution of rotation in models of massive single stars covering a wide range of masses and metallicities. These models reproduce very well observations during the early stages of the evolution (in particular WR populations and ratio between type II and type Ib,c at different metallicities, see Meynet & Maeder 2005). Our models predict the production of fast rotating black holes. Models with large initial masses or high metallicity end their life with less angular momentum in their central remnant with respect to the break-up limit for the remnant. Many WR star models satisfy the three main criteria (black hole formation, loss of hydrogen-rich envelope and enough angular momentum to form an accretion disk around the black hole) for gamma-ray bursts (GRB) production via the collapsar model (Woosley 1993). Considering all types of WR stars as GRB progenitors, there would be too many GRBs compared to observations. If we consider only WO stars (type Ic supernovae as is the case for SN2003dh/GRB030329, see Matheson et al. 2003) as GRBs progenitors, the GRBs production rates are in much better agreement with observations. WO stars are produced only at low metallicities in the present grid of models. This prediction can be tested by future observations.

Motivation & Objective

• To investigate how stellar rotation and metallicity affect the production of fast-rotating black holes and GRB progenitors.
• To resolve the discrepancy between predicted and observed GRB rates by identifying which WR star types are viable GRB progenitors.
• To test the collapsar model's viability for single massive stars by analyzing angular momentum retention and envelope loss.
• To examine the role of metallicity in WO star formation and its implications for GRB host galaxy properties.
• To provide a benchmark for future models including magnetic braking, which may further refine GRB rate predictions.

Proposed method

• Utilized the Geneva stellar evolution code with updated physics, including rotational mixing and metallicity-dependent mass loss.
• Tracked angular momentum evolution from main sequence to core collapse, focusing on central remnant spin and rotational breakup limits.
• Classified WR stars into types (WN, WC, WO) based on surface composition and evolutionary stage to assess GRB progenitor potential.
• Calculated GRB production rates by identifying models satisfying three collapsar criteria: BH formation, H-envelope loss, and sufficient angular momentum.
• Compared predicted GRB rates from all WR stars versus only WO stars against observational data to assess consistency.
• Assessed metallicity dependence of WO star formation, considering initial rotational velocity and angular momentum conservation.

Experimental results

Research questions

• RQ1 Which types of Wolf-Rayet stars are viable progenitors for long-soft gamma-ray bursts according to the collapsar model?
• RQ2 How do predicted GRB rates from all WR stars compare with observed rates, and why is there a discrepancy?
• RQ3 What is the metallicity dependence of WO star formation, and how does it affect GRB rate predictions?
• RQ4 Why do models with magnetic braking fail to produce sufficient angular momentum for GRBs, and how does this differ for WO stars?
• RQ5 Can single massive stars—without binary interactions—produce GRBs if WO stars are the only progenitors?

Key findings

• Models predict that only WO-type Wolf-Rayet stars, formed at low metallicities (Z ≈ Z_SMC), satisfy all three collapsar model criteria for GRB production.
• GRB production rates from all WR stars exceed observed rates by a large margin, indicating that not all WR stars can be GRB progenitors.
• When only WO stars are considered as progenitors, predicted GRB rates are in much better agreement with observational data.
• WO stars are only produced in the models at low metallicities, consistent with observations showing GRB host galaxies are metal-poor and blue.
• Stars with initial masses >50 M⊙ and low metallicity (Z ≈ Z_SMC) retain sufficient angular momentum in their central remnants to form GRBs.
• Magnetic braking is expected to be less effective for WO stars than for neutron star-forming stars due to their short lifetimes and lack of red supergiant phase, which may preserve angular momentum for GRB formation.