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Long GRB 260917C detected by Fermi GBM and AstroSat CZTI
AI Summary
Fermi GBM triggered on a long gamma-ray burst (GRB 260917C) on 2026-09-17 at 23:54:04 UT, localized to RA=155.6°, Dec=-46.8° with 5.2° statistical uncertainty. The burst was independently confirmed by AstroSat CZTI with a peak count rate of 101 counts/s in the 100-500 keV band and measured T90 duration of 32 seconds. Multiple Fermi GBM ground and flight position solutions were generated within ~90 seconds, though one early classification tentatively suggested AGN contamination (97% probability), indicating possible confusion with a known source in the field.
Measurements
| Event | GRB 260917C |
|---|---|
| Event ID | 811382049 |
| Source | Fermi GBM |
| Alert type | GRB |
| Significance | high |
| Trigger time (UTC) | Thu, 17 Sep 2026 23:54:04 GMT |
| Right ascension (J2000) | 155.6° |
| Declination (J2000) | -46.8° |
| Position error radius | 5.2° (5.20°) |
| Position from | Fermi-GBM position, GCN 45618 |
| GCN notices | 5 |
| GCN circulars | 2 |
Every localisation reported in Circulars (1)
| Instrument | Of | Error | Circular |
|---|---|---|---|
| Fermi-GBM | burst | 5.20° (1-sigma statistical) | GCN 45618 |
Observations (3)
Values parsed from the Circular text; each row names its Circular.
| Time since trigger | Band | Value | Telescope | Circular |
|---|---|---|---|---|
| — | 100-500 keV | 101 ± 53 counts/s | AstroSat | GCN 45689 |
| — | 100-500 keV | 1286 ± 366 counts | AstroSat | GCN 45689 |
| — | 100-500 keV | 533 ± 3 counts/s | AstroSat | GCN 45689 |
Notices (1)
Fermi GBM — GRB · Thu, 17 Sep 2026 23:54:04 GMT
GCN Circulars (2)
GCN-45689 — GRB 260917C
· Tue, 22 Sep 2026 06:02:22 GMT
A gamma-ray burst, GRB 260917C, was detected by the AstroSat CZTI instrument on September 17, 2026, at 23:54:04.17 UTC. The event was also detected by the Fermi GBM team, with a peak count rate of 101 counts/s above background in the 100-500 keV energy range.
GCN-45618 — GRB 260917C
· Fri, 18 Sep 2026 00:04:34 GMT
The Fermi Gamma-ray Burst Monitor (GBM) detected a likely long gamma-ray burst (GRB 260917C) on September 17, 2026, at 23:54:04 UT. The event was localized to RA = 155.6, Dec = -46.8 (J2000) with a statistical uncertainty of 5.2 degrees.
AI summary generated Tue, 13 Oct 2026 18:05:58 GMT.