A systematic search for long GRBs without supernovae: global properties and rate of events
Abstract
Some long duration gamma-ray bursts (LGRBs) are not associated with bright supernovae (SNe), indicating that their explosion mechanism differs from the traditional collapsar channel. SN-less LGRBs are rare, thus it remains unclear whether they are sporadic outliers or a substantial component of the GRB population. In this work, we use two decades of Swift observations to conduct a systematic search for nearby (z≲0.35) LGRBs without a confirmed SN association. Our analysis reveals a heterogeneous population linked, in part, to star-forming or dusty environments and, in part, to quiescent galaxies. Through the analysis of their high-energy properties, afterglows, and environments, we identify a sample of LGRBs with robust SN limits and distance scales, more than doubling the number of candidate SN-less events. From our fiducial sample, we derive a volumetric rate, not corrected for beaming, of R = (0.5 ± 0.2) ~Gpc−3 yr−1, comparable to the apparent rate of short duration GRBs (SGRBs) and standard LGRBs with SNe with luminosities L ≳ 1050 erg s−1. For plausible beaming factors, the inferred rate of SN-less LGRBs is consistent with several compact binary merger channels, although the allowed parameter space is already narrow if the entire population is attributed to a single progenitor channel. Owing to the small number of candidate events and the uncertainties in their distance scale, our sample leaves the low-luminosity tail unconstrained. A larger sample will be needed to determine whether they are the faint tail of known progenitor channels or evidence of a distinct route to relativistic explosions.
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BibTeX
@misc{yang2026systematic,
title = {{A systematic search for long GRBs without supernovae: global properties and rate of events}},
author = {Yu-Han Yang and Eleonora Troja and Nicolas Monsalves and Massine El Kabir and Narjes Shahamat Dehsorkh and Hira Waseem},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.20787},
eprint = {2609.20787},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.20787},
}
RIS
TY - UNPB
TI - A systematic search for long GRBs without supernovae: global properties and rate of events
AU - Yu-Han Yang
AU - Eleonora Troja
AU - Nicolas Monsalves
AU - Massine El Kabir
AU - Narjes Shahamat Dehsorkh
AU - Hira Waseem
PY - 2026
DA - 2026/09/17
PB - arXiv
DO - 10.48550/arxiv.2609.20787
UR - https://arxiv.org/abs/2609.20787
AB - Some long duration gamma-ray bursts (LGRBs) are not associated with bright supernovae (SNe), indicating that their explosion mechanism differs from the traditional collapsar channel. SN-less LGRBs are rare, thus it remains unclear whether they are sporadic outliers or a substantial component of the GRB population. In this work, we use two decades of Swift observations to conduct a systematic search for nearby (z≲0.35) LGRBs without a confirmed SN association. Our analysis reveals a heterogeneous population linked, in part, to star-forming or dusty environments and, in part, to quiescent galaxies. Through the analysis of their high-energy properties, afterglows, and environments, we identify a sample of LGRBs with robust SN limits and distance scales, more than doubling the number of candidate SN-less events. From our fiducial sample, we derive a volumetric rate, not corrected for beaming, of R = (0.5 ± 0.2) ~Gpc^−3 yr^−1, comparable to the apparent rate of short duration GRBs (SGRBs) and standard LGRBs with SNe with luminosities L ≳ 10^50 erg s^−1. For plausible beaming factors, the inferred rate of SN-less LGRBs is consistent with several compact binary merger channels, although the allowed parameter space is already narrow if the entire population is attributed to a single progenitor channel. Owing to the small number of candidate events and the uncertainties in their distance scale, our sample leaves the low-luminosity tail unconstrained. A larger sample will be needed to determine whether they are the faint tail of known progenitor channels or evidence of a distinct route to relativistic explosions.
ER -