TITLE: GCN CIRCULAR NUMBER: 43948 SUBJECT: Fermi GBM Sub-Threshold Detection of GRB 260307B DATE: 26/03/08 15:14:09 GMT FROM: Rushikesh Sonawane at IISER, TVM <rushikesh23@iisertvm.ac.in> R. Sonawane (IISER TVM), reports on behalf of the Fermi-GBM Team: SVOM/ECLAIRs detected the GRB 260307B on 2026-03-07 at 13:45:26 UTC (Magnani et al. 2026, GCN 43940). 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 a candidate. The GBM Targeted Search [1], the most sensitive coherent search for GRB-like signals in GBM, identified a transient starting at 2026-03-07T13:45:30.6 (UTC), most significantly on the 32 s timescale, with a false alarm rate of 2.5e-04 Hz. The Fermi-MET of this transient is 794583935.8 s. The Targeted Search localization is found to be spatially consistent with the SVOM/ECLAIRs localization. Additionally, the GBM Targeted Search event was found with the highest significance using a "soft" spectrum (Band function with Epeak = 70 keV, alpha = -1.9, beta = -3.7) for a GRB. [1] Goldstein et al. 2019 arXiv:1903.12597 View this GCN Circular online at https://gcn.nasa.gov/circulars/43948. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...