TITLE:   GCN CIRCULAR
NUMBER:  44029
SUBJECT: EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
DATE:    26/03/16 17:06:07 GMT
FROM:    mariaedvige.ravasio@ru.nl


M. E. Ravasio (ICE-CSIC and Radboud Univ.), P.G. Jonker (Radboud Univ.) 
and 
E. Burns (LSU), R. Hamburg (USRA), and P. Veres (UAH)

report on behalf of the Fermi-GBM Team:

Fermi-GBM had full spatial and temporal coverage of the transient EP260316a detected by EP-WXT (EP Team GCN 44027). There was no Fermi-GBM onboard trigger around the corrected EP starting time at T0 = 2026-03-16T12:33:13 UTC.

The GBM Targeted Search [1], the most sensitive, coherent search for GRB-like signals, was run in the time interval [-50;+500] s from T0, seeking signals between 64 ms and 32.768 s in duration. A faint transient signal was found most significantly at ~T0-3.6 s on a 4 s timescale, with a false alarm rate of 6.5e-05 Hz, although there is evidence of an earlier start of the emission at T0-20 s. The localisation is consistent with the EP one, with a spatial association probability of 98.8%. 
Among the three spectral templates tested, the transient was best-fit with a“soft” spectral template  (Band function with Epeak = 70 keV, alpha = -1.9, beta = -3.7) for a GRB.

[1] Goldstein et al. 2019 arXiv:1903.12597