TITLE: GCN CIRCULAR NUMBER: 36716 SUBJECT: Fermi GBM Sub-Threshold Detection of GRB 240619C DATE: 24/06/20 21:16:24 GMT FROM: sumanbala2210@gmail.com
S. Bala (USRA) reports on behalf of the Fermi-GBM Team:
AstroSat CZTI detected GRB 240619C at 2024-06-19 23:44:51.50 UTC (GCN 36711). There was a Fermi-GBM onboard accidental trigger around 420s before GRB 240619C. Due to the Fermi-GBM trigger latency, we were unable to trigger immediately on the GRB.
The GRB 240619C can be partially seen in the trigger data (trigger 740533060 / 240619984).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 340.68, Dec = -71.85 (J2000 degrees, equivalent to J2000 22h 43m, -71d 51'), with a statistical uncertainty of 1.15 degrees.
The angle from the Fermi LAT boresight is 56 degrees.
The GBM targeted search [1], the most sensitive, coherent search for GRB-like signals, was used to identify GRB-like emission episodes at around the AstroSAT GCN time. We find multiple emission peaks, each with a localization consistent with the on-ground localization from the Trigdat data. The brightest peak (at Fermi MET 740533496.5 s) was found to be the most significant (S/N of 15) on the 2.048 s timescale, with a false alarm rate of 5.4e-06 Hz, using the standard search protocol. The GBM targeted search found this brightest peak to have a "hard" GRB spectrum (Cut-off Power Law function with Epeak=1500 keV, alpha = -1.5 )
[1] Goldstein et al. 2019 arXiv:1903.12597
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