A new long gamma-ray burst formation pathway at solar metallicity

¹ Département d’Astronomie, Université de Genève, Chemin Pegasi 51, CH-1290 Versoix, Switzerland
² Gravitational Wave Science Center (GWSC), Université de Genève, CH-1211 Geneva, Switzerland
³ INAF – Osservatorio Astronomico di Brera, Via Emilio Bianchi 46, I-23807 Merate (LC), Italy
⁴ Istituto Nazionale di Fisica Nucleare – Sezione di Milano-Bicocca, piazza della Scienza 3, I-20126 Milano (MI), Italy
⁵ Institute of Astrophysics, Foundation for Research and Technology-Hellas, GR-71110 Heraklion, Greece
⁶ Department of Physics, University of Florida, 2001 Museum Rd, Gainesville, FL, 32611 USA
⁷ Institute for Fundamental Theory, 2001 Museum Rd, Gainesville, FL, 32611 USA
⁸ Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA), Northwestern University, 1800 Sherman Ave, Evanston, IL, 60201 USA
⁹ NSF-Simons AI Institute for the Sky (SkAI), 172 E. Chestnut St., Chicago, IL, 60611 USA
¹⁰ Institute of Space Sciences (ICE, CSIC), Campus UAB, Carrer de Magrans, 08193 Barcelona, Spain
¹¹ Institut d’Estudis Espacials de Catalunya (IEEC), Edifici RDIT, Campus UPC, 08860 Castelldefels (Barcelona), Spain
¹² Department of Physics and Astronomy, Northwestern University, 2145 Sheridan Road, Evanston, IL, 60208 USA
¹³ Electrical and Computer Engineering, Northwestern University, 2145 Sheridan Road, Evanston, IL, 60208 USA

^⋆ Corresponding author: max.briel@gmail.com

Received: 13 February 2025
Accepted: 30 June 2025

Abstract

Context. Long gamma-ray bursts (LGRBs) are generally observed in low-metallicity environments. However, 10% to 20% of LGRBs at redshift z < 2 are associated with near-solar to super-solar metallicity environments, remaining unexplained by traditional LGRB formation pathways that favor low metallicity progenitors.

Aims. In this work, we propose a novel formation channel for LGRBs that is dominant at high metallicities. We explore how a stripped primary star in a binary can be spun up by a second stable reverse-mass-transfer phase, initiated by the companion star.

Methods. We used POSYDON, a state-of-the-art population synthesis code that incorporates detailed single- and binary-star mode grids, to investigate the metallicity dependence of the stable reverse-mass-transfer LGRB formation channel. We determine the available energy to power an LGRB from the rotational profile and internal structure of a collapsing star and investigated how the predicted rate density of the proposed channel changes with different star formation histories and criteria for defining a successful LGRB.

Results. Stable reverse mass transfer can produce rapidly rotating, stripped stars at collapse. These stars retain enough angular momentum to account for approximately 10%–20% of the observed local LGRB rate density, under a reasonable assumption for the definition of a successful LGRB. However, the local rate density of LGRBs from stable reverse mass transfer can vary significantly, between 1 and 100 Gpc⁻³ yr⁻¹, due to strong dependencies on cosmic star formation rate and metallicity evolution, as well as the assumed criteria for successful LGRBs.