GRB 260223A

General information

GRB 260223A triggered Fermi/GBM at 2026-02-23 04:11:09 UT and was classified as a likely long GRB, with additional gamma-ray detections/characterization reported by SVOM/GRM, Glowbug (ISS), and GRID-11B. An uncatalogued optical transient consistent with the GRB localization was detected by DDOTI and subsequently confirmed by multiple optical facilities.

Wavelength coverage

• Gamma-ray: Detected/characterized by Fermi/GBM (including on-ground localization and spectral/fluence reporting), SVOM/GRM (T90 and spectral fits), Glowbug/ISS (timing, duration, significance), and GRID-11B (T90).
• Optical: MASTER-OAFA reported early upper limits; DDOTI detected a fading uncatalogued source; COLIBRÍ provided multi-band photometry and reported a brightening episode; 7DT detected the counterpart in r and several medium-band filters; SVOM/VT detected the counterpart and measured a decay slope; later COLIBRÍ detected continued fading. No observations were mentioned in X-ray, UV, near-IR (explicit), radio/mm, TeV, or neutrinos.

Lightcurve and spectrum

• Optical: DDOTI reported w(AB)=18.30±0.13 at T+14.9 min with estimated temporal decay ~-0.6; COLIBRÍ reported a continuous brightening with i rising from 18.55 to 18.15 over T+2.08 to +3.67 hr; SVOM/VT reported decay as a power law with index -1.1 during 11.40–15.14 hr; COLIBRÍ later measured r=20.93±0.07 at T+22.20 to +27.07 hr and inferred a decay slope ~-1.1 between epochs.
• Gamma-ray timing: SVOM/GRM T90=26(+8/-4) s (15–5000 keV); Fermi/GBM reported T90 ~39 s (50–300 keV); GRID-11B reported T90=22.2±3.0 s (30–2000 keV); Glowbug/ISS reported duration 20.5 s and total significance ~48.4 sigma, with two main peaks at ~T0+11 s and ~T0+18 s.
• Gamma-ray spectra: SVOM/GRM time-averaged cutoff power-law (index -1.29, Epeak=194 keV) and 1 s peak cutoff power-law (index -1.39, Epeak=741 keV); Fermi/GBM time-averaged Band fit (Epeak=70±6 keV, alpha=-0.76±0.09, beta=-1.91±0.02).

Redshift

What’s special vs typical

An early-time optical brightening phase was explicitly reported (COLIBRÍ i-band rise over ~2.1–3.7 hr post-trigger), in addition to later power-law decay measurements from independent facilities.