GRB 260226A: Bright long gamma-ray burst detected by Fermi and multiple observatories

AI Summary

A bright, long-duration gamma-ray burst (GRB 260226A) was detected on February 26, 2026 at 10:37:55 UT by Fermi GBM (trigger 793795080) and independently by Fermi-LAT at 10:38:18.84 UT, with refined position RA=41.93°, Dec=7.73° (error radius 0.11°). The burst exhibited structured multi-peaked emission with T90~82 seconds, peak photon flux of 166 ph/s/cm² (10-1000 keV), and spectral peak energy of 723 keV, with high-energy photons detected up to 1.1 GeV. The event was simultaneously detected by AstroSat CZTI, Konus-Wind, Insight-HXMT, NuSTAR, CALET, and Glowbug, making it exceptionally well-observed. Extensive optical follow-up observations from multiple ground-based telescopes (GROWTH-India, LCOGT, COLIBRÍ, Asiago, LAST, MASTER-Net) reported non-detections with limiting magnitudes between r~19.6 and r>22.86 AB, consistent with a faint or absent optical counterpart.

Measurements

Notices (2)

Fermi LAT — XRAY · Thu, 26 Feb 2026 10:38:18 GMT

Fermi GBM — GRB · Thu, 26 Feb 2026 10:37:55 GMT

GCN Circulars (18)

GCN-43878 — GRB 260226A · Sat, 28 Feb 2026 12:43:06 GMT
A team of astronomers led by A. Reguitti et al. reported no detection of a new source in the field of GRB 260226A using the 67/92 Schmidt Telescope at Asiago observatory. The non-detection was consistent with other reports and down to a limiting magnitude of r > 20.4 AB. The DESI Legacy survey was used for image subtraction.

GCN-43865 — GRB 260226A · Fri, 27 Feb 2026 16:11:28 GMT
Astronomical alert: GRB 260226A: Insight-HXMT/HE detection of the very bright burst

GCN-43864 — GRB 260226A · Fri, 27 Feb 2026 13:52:56 GMT
Astronomical alert: Konus-Wind detection of GRB 260226A

GCN-43860 — GRB 260226A · Fri, 27 Feb 2026 08:55:16 GMT
The CALET Gamma-Ray Burst Monitor detected a long gamma-ray burst, GRB 260226A, on February 26, 2026. The burst, which triggered multiple observatories, displayed a multi-peaked structure with T90 and T50 durations of 16.0 +/- 0.3 sec and 8.2 +/- 0.1 sec, respectively. The event was significant due to its detection by various observatories and the availability of ground-processed data.

GCN-43859 — GRB 260226A · Fri, 27 Feb 2026 06:16:42 GMT
A team of international researchers, led by Camila Angulo Valdez from UNAM, reported non-detection of a new source at the position of Fermi GRB 260226A using the DDRAGO imager on the COLIBRÍ telescope. They obtained 45 minutes of simultaneous exposures in the r and z filters and set 5-sigma upper limits on the magnitudes: r > 22.86 and z > 21.99. These limits are consistent with previous reports.

GCN-43858 — GRB 260226A · Fri, 27 Feb 2026 03:17:12 GMT
On February 27, 2026, a team led by R. Strausbaugh from Eastern Illinois University and A. Cucchiara from NASA observed the field of Fermi GRB 260226A using the LCOGT 1-meter Sinistro instrument at McDonald Observatory. No uncatalogued sources were detected within the Fermi LAT error region in the r and i bands. The team reported 5-sigma upper limits of r > 21.6 and i > 21.1, which are not corrected for galactic extinction.

GCN-43855 — GRB 260226A · Thu, 26 Feb 2026 20:34:03 GMT
The International Space Station's Glowbug gamma-ray telescope, operated by the US Naval Research Laboratory, detected GRB 260226A, a gamma-ray burst with a duration of 18.6 seconds and a total significance of 61.8 sigma. The burst was also detected by multiple other telescopes and observatories, including Fermi GBM, Fermi LAT, AstroSat CZTI, NuSTAR, and CALET. The light curve of the burst consisted of three primary peaks and three lesser peaks, with some detector deadtime affecting data around the 9.5-11 second mark. Preliminary analysis results are presented, but the response function used lacks detailed characterization of the ISS's passive structure.

GCN-43854 — GRB 260226A · Thu, 26 Feb 2026 20:10:43 GMT
The NuSTAR SINGS working group has detected bright prompt emission from long-duration GRB 260226A in both the NuSTAR CsI anti-coincidence shields. The detection, consistent with Fermi/GBM and AstroSat/CZTI observations, shows a single bright peak lasting for approximately 20 seconds with a peak count rate of ~14,000 cps and a baseline rate of ~1,000 cps. The emission is detected above 100 keV in the CdZnTe detectors, lasting for the same duration. The Fermi/LAT localization implies an offset from the NuSTAR boresight of 91 degrees and from the geocenter of 68 degrees.

GCN-43853 — GRB 260226A · Thu, 26 Feb 2026 19:55:15 GMT
A team of researchers led by IIT Bombay and Indian Institute of Astrophysics reported optical observations of GRB 260226A using the GROWTH-India Telescope 3.9 hours after the gamma-ray burst was detected by Fermi GBM and LAT. No new transients were detected within the observed region, and the results are consistent with other non-detection reports. The team covered about 74% of the localization area and used the r′ filter for each exposure with an exposure time of 300 seconds.

GCN-43852 — GRB 260226A · Thu, 26 Feb 2026 19:42:00 GMT
The Large Array Survey Telescope (LAST) collaboration reports no optical detection of GRB 260226A, as of 7.31 hours after the trigger, with a limiting magnitude of 20.15 AB. This non-detection is consistent with other optical observations and supports the fading of the gamma-ray burst.

GCN-43851 — GRB 260226A · Thu, 26 Feb 2026 16:21:05 GMT
On February 26, 2026, at 10:39:05 UT, the Fermi Gamma-ray Burst Monitor (GBM) detected a gamma-ray burst (GRB 260226A) with a duration of approximately 82 seconds and a peak photon flux of 166 ph/s/cm^2 in the 10-1000 keV energy range. The event was also observed by Fermi-LAT and AstroSat CZTI. The preliminary spectral analysis suggests a Band function with a peak energy of 723 keV.

GCN-43850 — GRB 260226A · Thu, 26 Feb 2026 16:15:30 GMT
On February 26, 2026, at 10:38:18.84 UT, Fermi-LAT detected high-energy emission from GRB 260226A, which was also observed by Fermi-GBM and Astrosat. The best on-ground location for this gamma-ray burst was determined to be RA, Dec = 41.93, 7.73 (J2000), with an error radius of 0.11 deg. The data from Fermi-LAT showed a significant increase in event rate correlated with the trigger, with a photon flux above 100 MeV of (1.50 ± 0.06)E-4 ph/cm2/s and an estimated photon index of -3.25 ± 0.08. The highest energy photon had an energy of 1.1 GeV and occurred at 420 seconds after the trigger.

GCN-43848 — GRB260226 · Thu, 26 Feb 2026 15:44:21 GMT
Astronomical alert: LAT GRB260226.44: Global MASTER-Net observations report

GCN-43847 — GRB 260226A · Thu, 26 Feb 2026 15:31:16 GMT
The MASTER-Net observatory, operated by a collaboration of institutions including Moscow State University and the Instituto de Astrofisica de Canarias, initiated observations of Fermi GRB 260226A using the MASTER-Tunka robotic telescope in Russia. The observations began approximately 11,000 seconds after the trigger time and covered various coordinates and exposure times. The team reported upper limits on the magnitude of the GRB in the clear filter, ranging from 17.9 to 19.1, depending on the exposure time and coaddition.

GCN-43846 — GRB 260226A · Thu, 26 Feb 2026 15:00:12 GMT
Astronomers using the AstroSat CZTI collaboration detected a bright long gamma-ray burst (GRB 260226A) in the 20-200 keV energy range. The burst was also detected by Fermi GBM, Fermi LAT, and Calet. The source was strongly detected in both CZT detectors and the CsI anticoincidence (Veto) detector. The CZTI team reported peak count rates, total counts, local mean background count rates, and T90 values for both detectors. The event was also reported to have 4947 Compton events associated with it.

GCN-43844 — GRB 260226A · Thu, 26 Feb 2026 13:34:45 GMT
A bright gamma-ray burst, GRB 260226A, was detected by the Fermi-LAT telescope at 10:38:18.84 UT on February 26, 2026. The burst was also detected by the GBM telescope but the trigger times differ due to the independent nature of the Fermi-LAT detection. The preliminary location of the burst is at RA 42.050, Dec +8.033, with an approximate error radius of 0.5 degrees. The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV and is the product of an international collaboration between NASA and DOE. This is only the second GRB to have passed the high threshold for LAT-seeded alerts.

GCN-43843 — GRB 260226A · Thu, 26 Feb 2026 13:23:46 GMT
A gamma-ray burst (GRB) with the designation GRB 260226A was detected by the Fermi Gamma-ray Burst Monitor (GBM) on February 26, 2026. The event was localized using the BALROG algorithm, with a best-fit position given by RA(2000.0) = 43.6 deg and Decl.(2000.0) = 9.6 deg, and a statistical error radius of 0.2 deg and a systematic error of 2 deg.

GCN-43840 — GRB 260226A · Thu, 26 Feb 2026 10:48:46 GMT
The Fermi Gamma-ray Burst Monitor (GBM) has detected and localized a new long gamma-ray burst (GRB), GRB 260226A, with a preliminary position given by RA = 45.3, Dec = 15.7, and a statistical uncertainty of 1.0 degrees. The angle from the Fermi Large Area Telescope (LAT) boresight is 17.0 degrees. This event is significant as gamma-ray bursts are the most powerful explosions in the Universe and provide valuable insights into astrophysical processes.