Blasts from the Past: UHECR Excesses from a Population of GRB 21009A-like Transients
Abstract
The most prominent feature in the ultra-high-energy cosmic ray (UHECR) sky is a significant excess of events from the vicinity of Centaurus A (Cen A). In this paper we investigate whether the excess may be caused by a past GRB 221009A-like event rather than Cen A itself. If an extraordinary gamma-ray burst (GRB) went off in one of the dwarf galaxies within the Cen A/M83 group, intergalactic magnetic deflections would naturally spread out and delay its cosmic ray signal, making it visible for ∼ 2× 105 years. Scaling this up, we model a local population of these exceptionally bright, narrow-jet transients within the \text{Greisen--Zatsepin--Kuzmin} (GZK) horizon. For a local volumetric rate of ṅ0≃4×10−8 Mpc−3 yr−1 and a jet half-opening angle of 0.8∘, we estimate ≃3−7 UHECR excesses across the sky at any given time. Varying the jet opening angle, GZK volume, and visibility time results in a broader range of excess values. It is possible to test this hypothesis by comparing the population predictions against existing and upcoming UHECR anisotropy data obtained by the Pierre Auger Observatory and the Telescope Array.
Related
- Expanding the Population of Short Gamma-Ray Transients with a Coherent Fermi/GBM Search. A 13-year catalog of short GRBs
- Radio Galaxies as UHECR Sources in Light of Recent Microquasar Results
- Self-confinement of ultra-high-energy nuclei in cosmic filaments: implications for the UHECR spectrum and composition
- Temporal Invariance Is an Illusion: Time-Dependent Influences of the Galactic Magnetic Field on UHECR Observations
- A Common ∼55 GeV Inelastic Dark Matter Origin of the LZ, Fermi-LAT, and AMS-02 Excesses and Paleo-Detector Prospects
BibTeX
@misc{mirabal2026blasts,
title = {{Blasts from the Past: UHECR Excesses from a Population of GRB 21009A-like Transients}},
author = {Nestor Mirabal},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.03886},
eprint = {2610.03886},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.03886},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Blasts from the Past: UHECR Excesses from a Population of GRB 21009A-like Transients
AU - Nestor Mirabal
PY - 2026
DA - 2026/10/02
PB - arXiv
DO - 10.48550/arxiv.2610.03886
UR - https://arxiv.org/abs/2610.03886
AB - The most prominent feature in the ultra-high-energy cosmic ray (UHECR) sky is a significant excess of events from the vicinity of Centaurus A (Cen A). In this paper we investigate whether the excess may be caused by a past GRB 221009A-like event rather than Cen A itself. If an extraordinary gamma-ray burst (GRB) went off in one of the dwarf galaxies within the Cen A/M83 group, intergalactic magnetic deflections would naturally spread out and delay its cosmic ray signal, making it visible for ∼ 2× 10^5 years. Scaling this up, we model a local population of these exceptionally bright, narrow-jet transients within the \text{Greisen--Zatsepin--Kuzmin} (GZK) horizon. For a local volumetric rate of ṅ_0≃4×10^−8 Mpc^−3 yr^−1 and a jet half-opening angle of 0.8^∘, we estimate ≃3−7 UHECR excesses across the sky at any given time. Varying the jet opening angle, GZK volume, and visibility time results in a broader range of excess values. It is possible to test this hypothesis by comparing the population predictions against existing and upcoming UHECR anisotropy data obtained by the Pierre Auger Observatory and the Telescope Array.
ER -