GCN Circular 45830
Subject
GRB 261007A: Fermi GBM observation
Event
Date
2026-10-07T09:55:08Z (14 hours ago)
From
Christian Malacaria at INAF-OAR <cmalacaria.astro@gmail.com>
Via
Web form
C. Malacaria (INAF-OAR) report report on behalf of the Fermi Gamma-ray Burst Monitor Team:
"At 05:39:49.71 UT on 07 October 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 261007A (trigger 813044394/261007236), which was also detected by SVOM/Eclairs (Hatsune Goto et al. 2026, GCN 45824), EP (W.F. Wen et al. 2026, GCN 45828), KAIT (W. Zheng et al. 2026, GCN 45825), and VLT (A. Saccardi et al. 2026, GCN 45829825) with a spectroscopic redshift of z = 2.101.
The Fermi GBM on-ground location is consistent with the SVOM/Eclairs position.
The angle from the Fermi LAT boresight is 92 degrees.
The GBM light curve consists of multiple bright peaks with a duration (T90) of about 22.8 s (50-300 keV).
The time-averaged spectrum from T0 to T0+36 s is best fit by a power law function with an exponential high-energy cutoff.
The power law index is -0.61 +/- 0.01 and the cutoff energy, parameterized as Epeak, is 300 +/- 4 keV.
The event fluence (10-1000 keV) in this time interval is (9.01 +/- 0.07)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+21.7 s in the 10-1000 keV band is 43.5 +/- 0.5 ph/s/cm^2.
A Band function fits the spectrum equally well with Epeak = 293 +/- 5 keV, alpha = -0.60 +/- 0.01 and beta = -3.3 +/- 0.3.
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/"