TITLE: GCN CIRCULAR NUMBER: 45366 SUBJECT: Fermi GBM Sub-Threshold Detection of GRB 260809A DATE: 26/08/12 19:55:21 GMT FROM: Bagrat Mailyan at Florida Tech <mbagrat@gmail.com> B. Mailyan (Florida Tech) reports on behalf of the Fermi-GBM Team: The SVOM/ECLAIRs detected GRB 260809A on 2026-08-09 at 14:57:33 UTC (Brunet et al. 2026, GCN 45331). There was no Fermi-GBM onboard trigger around this event time. An automated, blind search for gamma-ray bursts below the onboard triggering threshold in Fermi-GBM identified three candidates. The GBM Targeted Search [1], the most sensitive coherent search for GRB-like signals in GBM, identified a transient starting approximately 12 s after the ECLAIRs best image SNR time of 2026-08-09T14:57:13 UTC. The Targeted Search candidate was found most significantly on the 32 s timescale, with a false alarm rate of 1.6e-04 Hz. The Fermi-MET of the start time of this transient is 807980250.351 s. The Targeted Search localization is found to be spatially consistent with the ECLAIRs localization, with a spatial association probability of 95.8%. Additionally, the GBM Targeted Search event was found with the highest significance using a "normal" spectrum (Band function with Epeak = 230 keV, alpha = -1.0, beta = -2.3) for a GRB. The Targeted Search data release product for this event can be found here: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/targeted_search/trigger_repo... [1] Goldstein et al. 2019, arXiv:1903.12597 View this GCN Circular online at https://gcn.nasa.gov/circulars/45366. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...