General information
GRB 260131A triggered Fermi/GBM at 2026-01-31 06:39:30 UT and was reported as a likely long GRB with two separated emission episodes. A fading optical transient AT2026bwg (also reported as GOTO26akj / ZTF26aaemwcb) was identified as the afterglow, with consistent X-ray, NIR, and radio counterparts.
Wavelength coverage
- Gamma-rays: Fermi/GBM temporal and spectral analysis; Konus-Wind trigger and spectroscopy; Insight-HXMT/HE detection; GRID trigger and T90 measurement.
- X-rays: EP/FXT detected an uncatalogued X-ray source consistent with the optical afterglow position and reported a power-law spectrum.
- Optical: GOTO, COLIBRÍ, ZTF, P60/SEDM, NOT, GTC, FTW, KAIT, OHP/T193, Mondy/Terskol, ARIES DOT reported detections/monitoring and spectroscopy.
- Near-IR: SYSU 80cm reported a J-band detection.
- Radio: VLA detected an unresolved source at 6/10/15 GHz.
No observations mentioned in: UV, millimeter/sub-mm, TeV.
Lightcurve and spectrum
Redshift
The optical afterglow spectrum gives an absorption redshift z=1.434 from NOT/ALFOSC (Mg II, Fe II, Al III absorption), with an upper limit z<1.95 from continuum detected down to 3600 Å (lack of HI absorption). GTC/OSIRIS+ reports a consistent absorption system at z=1.435 and notes Fe II* lines.
What’s special vs typical
GCN 43963: GRB 260131A/B: radio detection with the VLA
2026-03-11T16:32:24.994Z | rev 0
GCN 43708: GRB260131A/B: 3.6m DOT Optical Observations
2026-02-12T07:33:33.029Z | rev 0
GCN 43670: GRB 260131A/B: continued Mondy optical observations
2026-02-09T15:13:09.897Z | rev 0
GCN 43632: GRB 260131A/B: Mondy and Terskol optical observations
2026-02-07T15:36:31.982Z | rev 0
GCN 43610: GRB 260131A/B: OHP/T193 optical observations
2026-02-03T14:29:32.069Z | rev 0
GCN 43609: GRB 260131A: KAIT optical observations
2026-02-03T07:55:33.094Z | rev 0
GCN 43607: GRB 260131A: FTW optical and NIR observations
2026-02-02T22:00:00.989Z | rev 3
GCN 43606: GRB 260131A/AT2026bwg: Observations by the Zwicky Transient Facility
2026-02-02T19:28:33.903Z | rev 0
2026-02-02T17:33:11.722Z | rev 0
GCN 43604: GRB 260131A/B: GTC/OSIRIS+ redshift confimation
2026-02-02T11:48:03.251Z | rev 0
GCN 43601: GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
2026-02-02T08:39:44.912Z | rev 0
GCN 43600: GRB 260131A/B: EP/FXT X-ray afterglow detection
2026-02-02T08:14:51.575Z | rev 0
GCN 43599: GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
2026-02-02T04:28:39.999Z | rev 0
GCN 43595: GRB 260131A: NOT spectroscopic redshift z = 1.434
2026-02-01T22:04:19.744Z | rev 0
GCN 43591: GRB 260131A: Insight-HXMT/HE detection
2026-02-01T15:06:33.922Z | rev 0
GCN 43590: Konus-Wind detection of GRB 260131A/B
2026-02-01T14:06:26.267Z | rev 0
GCN 43587: GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
2026-02-01T03:45:33.728Z | rev 0
GCN 43587: GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
2026-02-01T03:45:33.728Z | rev 2
GCN 43586: GRB 260131A/B: GOTO candidate optical counterpart consistent with the MAXI localisation
2026-01-31T23:32:35.393Z | rev 0
GCN 43585: GRB 260131A/B: Fermi GBM Observation
2026-01-31T23:12:56.781Z | rev 0
GCN 43579: GRB 260131A: Fermi GBM Final Real-time Localization
2026-01-31T06:50:08.998Z | rev 0