Radio follow up of a sub-threshold GRB in the sky localization area of GW241125

Gottschlich, Natalie, Corsi, Alessandra, Cenko, S. Bradley, Divyajyoti, Divyajyoti ORCID: https://orcid.org/0000-0002-2787-1012, DeLaunay, James, Fox, Derek B., O'Dwyer, Tanner and Ronchini, Samuele 2026. Radio follow up of a sub-threshold GRB in the sky localization area of GW241125. arXiv Cornell University. 10.48550/arXiv.2606.20885

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Abstract

Since the Fermi satellite’s identification of a candidate γ-ray burst (GRB) temporally coincident with GW150914, several tentative, and often debated, associations between electromagnetic (EM) transients and gravitational-wave (GW) signals from binary black hole (BBH) mergers have been reported. One such event, S241125n (later confirmed as GW241125 010116), was identified during the fourth observing run (O4) of Advanced LIGO and found to be spatially (within the large GW localization uncertainty) and temporally coincident with a subthreshold GRB detected by the Swift Burst Alert Telescope Gamma-ray Urgent Archiver for Novel Opportunities (BAT-GUANO). Here, we present results from a radio follow-up campaign targeting the BAT-GUANO localization region, carried out with the Karl G. Jansky Very Large Array (VLA). We also re-analyze Swift/XRT observations of the field, and combine these results with optical upper limits. Our analysis constrains the isotropic kinetic energy of a putative relativistic jet launched in the BBH merger to ≲ 3 × 10^50 erg for nISM = 1.0 cm^−3. We also discuss both the challenges and the diagnostic power of radio follow up in assessing candidate BBH–GRB associations, and present projections for analogous radio studies in the LIGO-Virgo-KAGRA observing run 5 (O5), and in the era of next-generation ground-based instrumentation. The enhanced sensitivity and localization capabilities of detector networks such as Cosmic Explorer and the Einstein Telescope, paired with the enhanced sensitivity of next-generation radio interferometers such as the next-generation VLA and the Square Kilometre Array, will significantly strengthen coordinated multi-messenger follow-up of BBHs. These next-generation facilities are likely to provide an answer to whether BBHs host relativistic ejecta powered by mini-disk accretion.

Item Type:	Working paper
Date Type:	Published Online
Status:	Submitted
Schools:	Schools > Physics and Astronomy
Subjects:	Q Science > QB Astronomy Q Science > QC Physics
Publisher:	Cornell University
Last Modified:	24 Jun 2026 08:45
URI:	https://orca.cardiff.ac.uk/id/eprint/187714

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