GCN 45685: GRB 260921B: Fermi GBM Final Localization
2026-09-21T23:19:25.336Z | rev 0
The Fermi GBM team reports the detection of a likely LONG GRB
"At 21:44:37.15 UT on 21 September 2026, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 260921B (trigger 811719882/260921906).
The on-ground calculated location, using the Fermi GBM trigger data,
is RA = 62.12, Dec = 31.21 (J2000 degrees, equivalent to J2000 4h 8m, +31d 12'),
with a statistical uncertainty of 2.22 degrees.
The angle from the Fermi LAT boresight is 107 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260921906/quicklook/glg_skymap_all_bn260921906.png
The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260921906/quicklook/glg_healpix_all_bn260921906.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260921906/quicklook/glg_lc_medres34_bn260921906.gif"
GCN 45671: EP260920b: SVOM/VT optical observation
2026-09-21T07:46:45.625Z | rev 2
H. L. Li, Y. N. Ma, C. Wu, L. P. Xin, Y. L. Qiu, Z. H. Yao, J. R. Xu, L. J. Chen, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, J. S. Deng, J. Y. Wei (NAOC), J. T. Palmerio (CEA/Irfu) report on behalf of the SVOM/VT team.
SVOM/VT performed ToO observation on the field of EP260920b (Ni et al., GCN 45664; Yang et al., GCN 45670). The observation started at 2026-09-21T01:24:03 UTC, about 11.3 hr after trigger in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously.
The optical counterpart (Liu et al., GCN 45668; García-García et al., GCN 45669) was detected in VT stacked images of both channels. The following measurements are in the AB magnitude and are not corrected for Galactic extinction:
Mid time | Band | Exposure Time | Magnitude (AB)
12.14 hr VT_B 55*50 sec 22.3 +/- 0.2
12.14 hr VT_R 48*50 sec 21.5 +/- 0.1
The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS.