TITLE:   GCN CIRCULAR
NUMBER:  42609
SUBJECT: Fermi GBM Sub-Threshold Detection of GRB 251106A
DATE:    25/11/07 03:05:39 GMT
FROM:    Matt Godwin <msg0028@uah.edu>

M. Godwin (UAH) and R. Hamburg (USRA) report on behalf of the Fermi-GBM Team:

SVOM/ECLAIRs detected GRB 251106A on 2025-11-06 at 19:56:37 UTC (Antier et al. 2025, GCN 42605). 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 roughly spatially-consistent candidate at 19:58:18.89 UTC.

The GBM Targeted Search [1], the most sensitive coherent search for GRB-like signals in GBM, also identified a transient spatially consistent with GRB 251106A  approximately 10 s before the SVOM trigger time. It is detected most significantly ~133 s after the SVOM trigger time on a 4.096 s timescale with a false alarm rate of 3.8e-5 Hz. The event was best-fit using a "normal" GRB spectrum (Band function with Epeak = 230 keV, alpha = -1.0, beta = -2.3). The Targeted Search localization is consistent with the SVOM/ECLAIRs location.

[1] Goldstein et al. 2019 arXiv:1903.12597