TITLE:   GCN CIRCULAR
NUMBER:  44273
SUBJECT: GRB 260410B: Fermi GBM Observation
DATE:    26/04/12 05:02:47 GMT
FROM:    rhamburg@usra.edu

R. Hamburg (USRA) and U. Pathak (IIT Bombay) report on behalf of the Fermi Gamma-ray Burst Monitor Team:

"At 12:22:26.93 UT on 10 April 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260410B (trigger 797516551/260410516), which was also detected by SVOM/GRM (Wang et al. 2026, GCN 44257).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 4.22, Dec = 37.74 (J2000 degrees, equivalent to J2000 0h 16m, +37d 44'), with a statistical uncertainty of 5.61 degrees (radius, 1-sigma containment, statistical only; there is additionally a systematic error which we have characterized as a mixture of two Gaussians, one with a radius of 1.8 degrees (52% contribution) and one with a radius of 4.1 degrees (47% contribution) [A. Goldstein et al. 2020, ApJ, 895, 1]).

The angle from the Fermi LAT boresight is 90 degrees.

The GBM light curve single bright emission episode with a duration (T90) of about 0.19 s (50-300 keV). The time-averaged spectrum from T0-0.04 to T0+0.16 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.01 +/- 0.09 and the cutoff energy, parameterized as Epeak, is 1220 +/- 30 keV.

The event fluence (10-1000 keV) in this time interval is (1.09 +/- 0.03)E-06 erg/cm^2. The 64-ms peak photon flux measured starting from T0+0.0 s in the 10-1000 keV band is 11.3 +/- 0.9 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/"