TITLE:   GCN CIRCULAR
NUMBER:  44861
SUBJECT: GRB 260607B: Fermi GBM Observation
DATE:    26/06/08 02:49:06 GMT
FROM:    eliza.neights@gmail.com

E. Neights (GWU, NASA GSFC) and E. Palafox (INAOE-Mexico) report on behalf of the Fermi Gamma-ray Burst Monitor Team:

"At 13:19:28.70 UT on 07 June 2026, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 260607B (trigger 802531173/260607555),
which was also detected by Fermi LAT (Holzmann Airasca et al. 2026, GCN 44860).
The Fermi GBM on-ground location is consistent with the Fermi LAT position.

The angle from the Fermi LAT boresight is 72 degrees.

The GBM light curve consists of multiple emission episodes, with a duration (T90)
of about 47 s (50-300 keV). The time-averaged spectrum
from T0+2.9 to T0+57.1 s is best fit by
a power law function with an exponential high-energy cutoff.
The power law index is -0.92 +/- 0.004 and the cutoff energy,
parameterized as Epeak, is 728 +/- 2 keV.

The event fluence (10-1000 keV) in this time interval is
(2.999 +/- 0.006)E-04 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+53 s in the 10-1000 keV band is 66.9 +/- 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/"