GCN 45642: EP260917a: SVOM/VT optical upper limits
2026-09-19T09:03:02.919Z | rev 0
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 EP260917a (Huang et al., GCN 45621). The observation started at 2026-09-18T03:23:30 UTC, 17.8 hours after trigger in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously.
No credible uncatalogued candidates were identified in our stacked images within the error box of EP-WXT (Huang et al., GCN 45621) compared to the Legacy Survey.
The following measurements are in the AB magnitude and are not corrected for Galactic extinction:
Mid time | Band | Exposure Time | 5-sigma upper limit
18.0 hr VT_B 23*50 sec > 22.8 mag
18.0 hr VT_R 23*50 sec > 22.7 mag
Our results are consistent with the non-detections from COLIBRÍ (Guelfand et al., GCN 45624) and WINTER (Mohan et al., GCN 45628).
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.
GCN 45613: GRB 260917A: Glowbug gamma-ray detection
2026-09-17T15:22:35.147Z | rev 0
C.C. Cheung, R. Woolf, M. Kerr, J.E. Grove (NRL), A. Goldstein (USRA), C.A. Wilson-Hodge, D. Kocevski (MSFC), and M.S. Briggs (UAH) report:
The Glowbug gamma-ray telescope [1,2,3], operating on the International Space Station, confirms the detection of GRB 260917A, which was detected by Fermi/GBM (GCN 45603, 45604).
The burst onset is at 2026-09-17 02:24:07.4 with a burst duration of ~8.5 s. The detection occurred during a time of high background as Glowbug was in the southern radiation belt. The lightcurve comprises a single peak corresponding to the first, brightest peak observed in the Fermi/GBM lightcurve.
The analysis results presented here are preliminary and use a response function that lacks a detailed characterization of the surrounding passive structure of the ISS.
Glowbug is a NASA-funded technology demonstrator for sensitive, low-cost gamma-ray transient telescopes developed, built, and operated by the U.S. Naval Research Laboratory (NRL) with support from the University of Alabama in Huntsville, USRA, and NASA MSFC. It was launched on 2023 March 15 aboard the Department of Defense Space Test Program’s STP-H9 to the ISS and operated until 2024 April when it was put in safe storage on orbit. Glowbug was removed from storage and resumed operation on 2025 September 12.
[1] Grove, J.E. et al. 2020, Proc. Yamada Conf. LXXI, arXiv:2009.11959
[2] Woolf, R.S. et al. 2022, Proc. SPIE, 12181, id. 121811O
[3] Woolf, R.S. et al. 2024, Proc. SPIE, 13151, id. 1315108
Distribution Statement A: Approved for public release. Distribution is unlimited.
GCN 45604: GRB 260917A: BALROG localization (Fermi Trigger 811304653 / GRB 260917100)
2026-09-17T02:57:11.656Z | rev 0
T. Preis (University of Innsbruck) & J. Greiner (MPE Garching) report:
The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger
811304653 at 02:24:08 on 17 Sept. 2026 were automatically fitted for spectrum
and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427;
Berlato et al. 2019, ApJ 873, 60).
The best-fit position is:
RA(2000.0) = 310.2 deg
Decl.(2000.0) = -31.9 deg
The 1 sigma statistical error radius is 1.4 deg.
We estimate an additional systematic error of 1 deg.
Further details are available at:
https://grb.mpe.mpg.de/grb/GRB260917100/
The Healpix map can be downloaded from:
https://grb.mpe.mpg.de/grb/GRB260917100/healpix
The location parameters are available as JSON at:
https://grb.mpe.mpg.de/grb/GRB260917100/json
GCN 45603: GRB 260917A: Fermi GBM Final Real-time Localization
2026-09-17T02:34:35.898Z | rev 0
The Fermi GBM team reports the detection of a likely LONG GRB
At 02:24:08 UT on 17 Sep 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260917A (trigger 811304653.400746 / 260917100).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 311.6, Dec = -32.8 (J2000 degrees, equivalent to J2000 20h 46m, -32d 47'), with a statistical uncertainty of 1.7 degrees.
The angle from the Fermi LAT boresight is 121.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260917100/quicklook/glg_skymap_all_bn260917100.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/bn260917100/quicklook/glg_healpix_all_bn260917100.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260917100/quicklook/glg_lc_medres34_bn260917100.gif