GCN Circular 30420
Subject
Fermi GBM Sub-Threshold Detection of GRB 210707A
Event
Date
2021-07-08T16:49:47Z (4 years ago)
From
Cori Fletcher at USRA <cfletcher@usra.edu>
C. Fletcher (USRA) reports on behalf of the Fermi-GBM Team:
INTEGRAL/IBAS detected GRB 210707A at 22:25:05 UT (GCN 30414). There was no
Fermi-GBM onboard trigger around the event.
An automated, blind search for short gamma-ray bursts below the onboard
triggering threshold in Fermi-GBM identified no counterparts.
The GBM targeted search [1], the most sensitive, coherent search for
GRB-like signals identified a transient most significantly on the 8.192 s
timescale, with a false alarm rate of 6.4e-06 Hz and a location consistent with
the INTEGRAL/IBAS event, using the standard search protocol with a S/N of 15.
The GBM targeted search event was found with the highest
significance with a "norm" spectrum (Band function with
Epeak = 230 keV, alpha = -1.0, beta = -2.3) for a GRB.
[1] Goldstein et al. 2019 arXiv:1903.12597