STARITHM
Long GRB 260921A detected by Fermi GBM with optical counterpart identified
AI Summary
Fermi GBM triggered on a likely long gamma-ray burst (GRB 260921A) at 09:29:08 UT on September 21, 2026, with localization RA=148.9°, Dec=0.6° and statistical uncertainty of 1.4°. The burst showed complex structure with ~10 second duration and peak count rate of ~4500 counts/sec (15-350 keV). MASTER-OAFA robotic telescope detected optical counterpart MASTER OT J094129.58+025052.5 at magnitude ~14 associated with a host galaxy at redshift z=1.3, confirming the astrophysical nature of the event.
Measurements
| Event ID | 811675753 |
|---|---|
| Source | Fermi GBM |
| Alert type | GRB |
| Significance | high |
| Trigger time (UTC) | Mon, 21 Sep 2026 09:29:08 GMT |
| Right ascension (J2000) | 148.87° |
| Declination (J2000) | 0.58° |
| Position error radius | 1.41° |
| GCN notices | 5 |
| GCN circulars | 4 |
Notices (1)
Fermi GBM — GRB · Mon, 21 Sep 2026 09:29:08 GMT
GCN Circulars (4)
GCN-45678 — GRB 260921A
· Mon, 21 Sep 2026 10:29:29 GMT
The MASTER-OAFA robotic telescope detected a possible optical counterpart, MASTER OT J094129.58+025052.5, to the gamma-ray burst Swift GRB 260921A, with a magnitude of approximately 14. This detection is associated with a host galaxy at a redshift of z=1.3.
GCN-45677 — GRB 260921A
· Mon, 21 Sep 2026 09:59:36 GMT
The MASTER-OAFA robotic telescope in Argentina observed the Swift GRB 260921A error box starting 80 seconds after the trigger, with upper limits up to 15.5 magnitude. Observations were conducted under twilight conditions, and the data is being continuously updated and analyzed.
GCN-45676 — GRB 260921A
· Mon, 21 Sep 2026 09:52:28 GMT
The Swift Burst Alert Telescope (BAT) detected a gamma-ray burst, GRB 260921A, on September 26, 2021, at 09:29:12 UT. The burst had a complex structure with a duration of about 10 seconds and a peak count rate of approximately 4500 counts/sec. Swift's automatic slews are currently disabled, and the burst is Sun-constrained until October 8, 2021, preventing further XRT or UVOT data collection.
GCN-45674 — GRB 260921A
· Mon, 21 Sep 2026 09:39:40 GMT
The Fermi Gamma-ray Burst Monitor (GBM) detected a likely long gamma-ray burst (GRB 260921A) on September 21, 2026, at 09:29:08 UT. The event was located at RA = 148.9, Dec = 0.6 (J2000) with a statistical uncertainty of 1.4 degrees.
AI summary generated Mon, 21 Sep 2026 12:02:16 GMT.