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GCN Circular 32269

Subject
GRB 220624A: Fermi GBM Detection
Date
2022-06-25T15:25:40Z (2 years ago)
From
Stephen Lesage at Fermi-GBM Team <sjl0014@uah.edu>
S. Lesage (UAH) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray
Burst Monitor Team:

"At 02:58:35 UT on 24 June 2022, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 220624A (trigger 677732320/220624124)
which was also detected by AGILE (A. Ursi, et al. 2022, GCN 32259),
Swift/BAT-GUANO (A. Tohuvavohu et al., GCN 32263),
and localized by IPN (A. S. Kozyrev et al. 2022, GCN 32265).
The Fermi GBM Final Real-time Localization (GCN 32256) is consistent with
the IPN triangulation.

The angle from the Fermi LAT boresight is 86 degrees.

The GBM light curve shows two bright emission episodes
and one faint emission episode with a duration (T90)
of about 285 s (10-1000 keV).

The time-averaged spectrum for the first emission episode
from T0-0.5 to T0+59.9 s is best fit by
a Band function with Epeak = 486 +/- 12 keV,
alpha = -0.75 +/- 0.01, and beta = -2.39 +/- 0.06.
The event fluence (10-1000 keV) in this time interval is
(1.550 +/- 0.001)E-04 erg/cm^2.

The time-averaged spectrum for the second emission episode
from T0+137.7 to T0+172.5 s is best fit by
a power law function with an exponential high-energy cutoff.
The power law index is -1.23 +/- 0.06 and the cutoff energy,
parameterized as Epeak, is 132 +/- 8 keV.
The event fluence (10-1000 keV) in this time interval is
(1.19 +/- 0.04)E-05 erg/cm^2.
A Band function fits the spectrum equally well
with Epeak= 124 +/- 11 keV, alpha = -1.19 +/- 0.07 and beta = -2.8 +/- 0.5.

The time-averaged spectrum for the third emission episode
from T0+285.2 to T0+333.3 s is best fit by
a Band function with Epeak = 61 +/- 10 keV,
alpha = 1.3 +/- 1.0, and beta = -2.0 +/- 0.1.
The event fluence (10-1000 keV) in this time interval is
(7.3 +/- 0.5)E-06 erg/cm^2.

The 1-sec peak photon flux measured starting from T0+6.0 s
in the 10-1000 keV band is 39.1 +/- 0.5 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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