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GCN Circular 31856

Subject
GRB 220408A: Fermi GBM observation
Date
2022-04-08T17:49:46Z (2 years ago)
From
Elisabetta Bissaldi at INFN,Bari <elisabetta.bissaldi@ba.infn.it>
E. Bissaldi (Politecnico and INFN Bari) reports on behalf of the Fermi GBM 
Team:


"At 05:46:04.41 UT on 8 April 2022, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 220408A (trigger 671089569/ 220408240), which was also detected by the Swift/BAT (Caputo et al. 2022, GCN 31848). 
The Fermi GBM Final Real-time Localization (GCN 31847) is consistent with the Swift position.

The angle from the Fermi LAT boresight at the GBM trigger time is 57 degrees. 

The GBM light curve consists of a multipeaked emission episode with a duration (T90) of about 20 s (50-300 keV).
The time-averaged spectrum from T0-0.8 s to T0+6.7 s is well fit by a power law function with an exponential high-energy cutoff. The power law index is -0.72 +/- 0.14 and the cutoff energy, parameterized as Epeak, is 48.8 +/- 2.3 keV.

The event fluence (10-1000 keV) in this time interval is (1.33 +/- 0.05)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+2.4 s in the 10-1000 keV band is 7.7 +/-0.3 ph/s/cm^2. 


The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: 
https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html

For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"
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