GCN 45689: GRB 260917C: AstroSat CZTI detection
2026-09-22T06:02:22.291Z | rev 0
Harsha K. H. (IUCAA), S. Salunke(IUCAA), A. Goyal (IITB), A. Arya (IITB), G. Waratkar (CalTech/IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration:
Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a GRB 260917C which was also detected by Fermi (Fermi GBM team, GCN Circ. 45618).
The source was clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2026-09-17 23:54:04.17 UTC.The measured peak count rate associated with the burst is 101 (+53, -2) counts/s above the background in the combined data of three quadrants (out of four), with a total of 1286 (+366, -401) counts. The local mean background count rate was 533 (+3, -4) counts/s. We measure a T90 of 32 (+5, -8) s from the cumulative Veto light curve.
CZTI data products like interactive and downloadable light curves for this GRB can be found at: https://astrosat.iucaa.in/cift/cift_products/ET20260917T235404/ET20260917T235404_details.html
CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project.
CZTI GRB detections are reported regularly on the payload site at:
http://astrosat.iucaa.in/czti/?q=grb
GCN 45618: GRB 260917C: Fermi GBM Final Real-time Localization
2026-09-18T00:04:34.516Z | rev 0
The Fermi GBM team reports the detection of a likely LONG GRB
At 23:54:04 UT on 17 Sep 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260917C (trigger 811382049.420122 / 260917996).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 155.6, Dec = -46.8 (J2000 degrees, equivalent to J2000 10h 22m, -46d 47'), with a statistical uncertainty of 5.2 degrees.
The angle from the Fermi LAT boresight is 103.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260917996/quicklook/glg_skymap_all_bn260917996.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/bn260917996/quicklook/glg_healpix_all_bn260917996.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260917996/quicklook/glg_lc_medres34_bn260917996.gif