TITLE:   GCN CIRCULAR
NUMBER:  46002
SUBJECT: GRB 261020A: Fermi GBM Observation
DATE:    26/10/21 05:36:47 GMT
FROM:    Marianna Dafčíková at Masaryk University <500025@mail.muni.cz>

M. Dafcikova (MUNI) reports on behalf of the Fermi Gamma-ray Burst Monitor Team:

"At 05:37:08.94 UT on 20 October 2026, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 261020A (trigger 814167433/261020234),
which was also detected by MAXI GSC (T. Kato et al. 2026, GCN 45993).
The Fermi GBM on-ground location is consistent with the MAXI position.

The angle from the Fermi LAT boresight is 89 degrees.

The GBM light curve consists of an emission episode with a duration (T90)
of about 114 s (50-300 keV). The time-averaged spectrum
from T0-22 to T0+98 s is best fit by
a power law function with an exponential high-energy cutoff.
The power law index is -0.76 +/- 0.06 and the cutoff energy,
parameterized as Epeak, is 1000 +/- 70 keV.

The event fluence (10-1000 keV) in this time interval is
(1.47 +/- 0.06)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+3.6 s in the 10-1000 keV band is 3.1 +/- 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/"