GCN Circular 37493
Subject
EP240913a: A GRB Event
Date
2024-09-14T04:10:41Z (3 months ago)
Edited On
2024-09-14T13:57:29Z (3 months ago)
From
Iris Yin at Nanjing University <iris.yin@smail.nju.edu.cn>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of Iris Yin at Nanjing University <iris.yin@smail.nju.edu.cn>
Via
Web form
Yi-Han Iris Yin (NJU), Jun Yang (NJU), Bin-Bin Zhang (NJU), Hui Sun (NAOC) and Xuefeng Wu (PMO) report on behalf of large collaboration:
Our team has conducted a follow-up high-energy data search of the X-ray transient detected by the Einstein Probe (EP) at 2024-09-13T11:39:33 UTC (EP240913a; GCN Circular 37492). We discovered a bright gamma-ray transient in the Fermi/GBM data approximately 180 seconds after T0 of EP240913a, coinciding with the peak time of the X-ray transient. Additionally, we note that this event is listed as a burst trigger (bn240913488) in the GBM database.
The GBM light curve shows a single emission episode with a duration (T90) of approximately 5 seconds (10-1000 keV). The time-averaged spectrum from T0+181 to T0+188 seconds is well fitted by a cutoff power-law function, N(E) = A*(E^-Gamma)*exp(-E*(2-Gamma)/Ep), with a peak energy of about 100 keV and a photon index, Gamma, of approximately 0.5. The fluence (10-1000 keV) during this interval is estimated to be ~ 1.88e-6 erg/cm^2, and the 0.26-s binned peak flux in the 10-1000 keV band is ~ 1.74e-6 erg/s/cm^2.
Given that the gamma-ray transient is consistent with EP240913a in both timing and location, we propose that this is a GRB event.
We strongly recommend further follow-up observations of EP240913a to confirm its physical nature and to search for potential afterglows.