TITLE: GCN CIRCULAR NUMBER: 39600 SUBJECT: EP250304A: Upper limits from Fermi-GBM Observations DATE: 25/03/06 09:13:06 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:
At the starting time T0=2025-03-04T01:29:49 UTC of the EP-WXT event EP250304A (Zhang et al., GCN 39591), Fermi was in South Atlantic Anomaly (SAA). Fermi-GBM had exited SAA approximately 50 seconds after T0. There was no Fermi-GBM onboard trigger around EP-WXT time.
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 3.9e-08 erg/cm2/s in the energy band 10-1000 keV.
[1] Goldstein et al. 2019 arXiv:1903.12597
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