GCN Circular 45961
Subject
GRB 261010A: VLA radio observations
Event
Date
2026-10-16T14:30:05Z (4 days ago)
From
Genevieve Schroeder at Cornell University <genevieveschroeder@u.northwestern.edu>
Via
Web form
G. Schroeder (U. Toronto), W. Fong (Northwestern), J. Rastinejad (UMD), Gokul Srinivasaragavan (Northwestern) report:
We observed the location of GRB 261010A (Fermi GBM team, GCN 45888; Lien et al., GCN 45889; Frederiks et al., GCN 45925, Cheung et al., GCN 45950) with the Karl G. Jansky Very Large Array (VLA) in D configuration under program 26A-062 (PI Schroeder) for 0.75 hour at a mean frequency of 10 GHz and mid time of 2026 Oct 15 at 23:40 UT (5.1 days post-burst).
In preliminary analysis, we do not detect any radio sources at or near the position of the afterglow (Osborne et al., GCN 45894, O’Neill et al., GCN 45890; Aceituno et al., GCN 45891; Corcoran et al., GCN 45912), to a 3-sigma limit of < 20 microJy.
At z=0.070 (Corcoran et al., GCN 45912) this limit corresponds to a rest-frame luminosity of < 2e27 erg/s/Hz. This luminosity limit is 1-2 orders of magnitude lower than the typical range for radio detected short GRBs (e.g., Anderson et al. 2025) and an order of magnitude deeper than the strongest radio limits on short GRBs. This limit is also ~4 times lower than the long merger-driven GRB 230307A (e.g. Levan et al. 2024), but similar to limits placed on the long merger-driven GRB 211211A (e.g. Rastinejad et al. 2022). At z=0.785 (Castro-Tirado et al., GCN 45928), this corresponds to a rest-frame luminosity of < 3e29 erg/s/Hz. This luminosity limit is comparable to limits placed on short GRBs with no radio detections, but is about an order of magnitude lower than the typical range for long GRBs from collapsars (e.g. Chandra and Frail 2012).
Further observations are planned. We thank the VLA staff for quickly approving and executing these observations.