GCN Circular 33766

C. Malacaria (ISSI) and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:

"At 12:04:06.93 UT on 10 April 2023, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 230510A (trigger 705413051 / 230510503), which
was also detected by the Swift/BAT and Swift/XRT (Eyles-Ferris et al. 2023,
GCN 33752
Not found
 
 
; Evans et al. 2023, GCN 33756
Not found
 
 
). The GBM on-ground location is
consistent with the Swift position (GCN 33751
Not found
 
 
).

The angle from the Fermi LAT boresight at the GBM trigger time is 14
degrees.

The GBM light curve shows a weaker peak followed about 100 s later
by a brighter peak, with a duration (T90) of about 177 s (50-300 keV).
The time-averaged spectrum from T0-4.1 s to T0+11.3 s is
best fit by a power law function with an exponential
high-energy cutoff. The power law index is -0.9 +/- 0.1 and
the cutoff energy, parameterized as Epeak, is 87 +/- 7 keV.
A Band function fits the spectrum equally well
with Epeak = 87 +/- 9 keV, alpha = -0.9 +/- 0.1 and beta = -3.8 +/- 3.2.

The event fluence (10-1000 keV) in this time interval is
(2.0 +/- 0.1)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+158 s in the 10-1000 keV band
is 12.4 +/- 0.4 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/"