Constraints on the central engine of merger-driven long gamma-ray bursts
Abstract
Recent observations have identified a new class of long-duration gamma-ray bursts (GRBs) likely produced by compact binary mergers. Using radio observations and lightcurve modelling, we investigate whether a magnetar remnant can power the long-lasting prompt emission observed in this merger-driven GRB sample. We derive constraints on the magnetars' rotational energy and magnetic-field strength, and assess whether the magnetar central-engine model is viable for the observed events. We conducted 2.1 GHz radio observations of seven nearby merger-driven GRBs (z<0.25) using the Australia Telescope Compact Array (ATCA), obtaining sensitive upper limits on late-time radio emission 520-6900 days post-burst. We modelled the expected radio light curves from magnetar-energized ejecta interacting with the circumburst medium and compared them to our observations. We separately tested the magnetar hypothesis against the extended gamma-ray emission using a fallback-accreting magnetar model. No radio counterpart is detected in any of the observed GRBs, with 3σ flux density upper limits of 33-72 μJy at 2.1 GHz. Modelling the expected synchrotron emission from magnetar-energized ejecta interacting with the circumburst medium, we find that the radio non-detections remain compatible with energetic outflows in low-density environments. The analysis of the prompt gamma-ray emission provides complementary constraints on the spin period and magnetic field of the magnetar engine. Once fallback accretion and jet baryon-loading are considered, the parameter space is narrowly confined.
Related
- Multimessenger Constraints on the Central Engine in SN 2023ixf: Neutron Star or Black Hole?
- Prompt and Afterglow Constraints on the Central Engine of GRB 240825A
- The Milky Way’s Early Disk Was Built in Bursts. I. Evidence from Low-angular-momentum, High- α Stars Scattered Out of the Protodisk by Merger Events
- The Milky Way's Early Disk Was Built in Bursts. I. Evidence from Low-angular-momentum, High-α Stars Scattered Out of the Protodisk by Merger Events
- Joint Constraints on the Hubble Constant and Cosmic Baryon Density from Localized Fast Radio Bursts and DESI DR2 Baryon Acoustic Oscillations
BibTeX
@misc{yadav2026constraints,
title = {{Constraints on the central engine of merger-driven long gamma-ray bursts}},
author = {Muskan Yadav and Roberto Ricci and Paz Beniamini and Hira Waseem and Tatsuya Matsumoto and Simone Dichiara and Eleonora Troja},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.17507},
eprint = {2609.17507},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.17507},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Constraints on the central engine of merger-driven long gamma-ray bursts
AU - Muskan Yadav
AU - Roberto Ricci
AU - Paz Beniamini
AU - Hira Waseem
AU - Tatsuya Matsumoto
AU - Simone Dichiara
AU - Eleonora Troja
PY - 2026
DA - 2026/09/15
PB - arXiv
DO - 10.48550/arxiv.2609.17507
UR - https://arxiv.org/abs/2609.17507
AB - Recent observations have identified a new class of long-duration gamma-ray bursts (GRBs) likely produced by compact binary mergers. Using radio observations and lightcurve modelling, we investigate whether a magnetar remnant can power the long-lasting prompt emission observed in this merger-driven GRB sample. We derive constraints on the magnetars' rotational energy and magnetic-field strength, and assess whether the magnetar central-engine model is viable for the observed events. We conducted 2.1 GHz radio observations of seven nearby merger-driven GRBs (z<0.25) using the Australia Telescope Compact Array (ATCA), obtaining sensitive upper limits on late-time radio emission 520-6900 days post-burst. We modelled the expected radio light curves from magnetar-energized ejecta interacting with the circumburst medium and compared them to our observations. We separately tested the magnetar hypothesis against the extended gamma-ray emission using a fallback-accreting magnetar model. No radio counterpart is detected in any of the observed GRBs, with 3σ flux density upper limits of 33-72 μJy at 2.1 GHz. Modelling the expected synchrotron emission from magnetar-energized ejecta interacting with the circumburst medium, we find that the radio non-detections remain compatible with energetic outflows in low-density environments. The analysis of the prompt gamma-ray emission provides complementary constraints on the spin period and magnetic field of the magnetar engine. Once fallback accretion and jet baryon-loading are considered, the parameter space is narrowly confined.
ER -