GCN Circular 36416

B. Mailyan (Florida tech) and C. Meegan (UAH) report on behalf of
the Fermi Gamma-ray Burst Monitor Team:

"At 05:12:52.64 UT on 04 May 2024, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 240504A (trigger 736492377/240504217).
which was also detected by Swift/BAT-GUANO (S. Ronchini et al. 2024, GCN 36401
Not found
 
 
).
The Fermi GBM on-ground location is consistent with the Fermi GBM final position notice (GCN 36387
Not found
 
 
).

The angle from the Fermi LAT boresight is 64 degrees.

The GBM light curve consists of a single emission episode with a duration (T90)
of about 19 s (50-300 keV). The time-averaged spectrum
from T0+0.003 to T0+20.096 s is best fit by
a power law function with an exponential high-energy cutoff.
The power law index is -1.12 +/- 0.02 and the cutoff energy,
parameterized as Epeak, is 682.50 +/- 52.10. 
A Band function with Epeak 665.80 +/- 55.40, Alpha -1.11 +/- 0.02, Beta -3.01 +/- 0.77 fits the spectrum equally well. 

The event fluence (10-1000 keV) in this time interval is
(2.26 +/- 0.03)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+6.7 s in the 10-1000 keV band is 11.5 +/- 0.3 ph/s/cm^2.

We note that there is a second FRED-like peak about 100s after the reported event here that seems to be related. 
However, due to a contemporaneous solar flare, we are unable to disentangle the two events and thus we omit this 
portion of the burst due to contamination. We note that the burst could have a T90 of 250s, but other instruments are required to confirm this.

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/"