TITLE: GCN CIRCULAR NUMBER: 39537 SUBJECT: EP250223A: Upper limits from Fermi-GBM Observations DATE: 25/02/28 17:47:57 GMT FROM: mariaedvige.ravasio@ru.nl

M. E. Ravasio (Radboud Univ.), E. Burns (LSU), and P.G. Jonker (Radboud Univ.) report on behalf of the Fermi-GBM Team:

Fermi-GBM had full spatial coverage of the transient EP250223A detected by EP-WXT (Lian et al., GCN 39429). There was no Fermi-GBM onboard trigger around the EP starting time T0=2025-02-23T15:02:05.66 UTC (Wang et al., GCN 39448).

The GBM targeted search [1], the most sensitive, coherent search for GRB-like signals, was run in the time interval [T0-50;T0+500] s, seeking signals between 64 ms and 32.768 s in duration. No signal consistent with the EP transient both temporally and spatially is identified, as confirmed by visual inspection of the data.

Assuming a “soft” spectral template (Band function with Epeak = 70 keV, alpha = -1.9, beta = -3.7), and a duration of 8.192 s, we derive a sky-averaged flux upper limit of 3.1e-08 erg/cm2/s in the energy band 10-1000 keV.

[1] Goldstein et al. 2019 arXiv:1903.12597

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