General information
GRB 260125A was detected by Fermi/GBM and is reported as a likely long GRB. Optical follow-up identified a fading transient candidate (AT 2026bjf / GOTO26acv) within the GBM localization, while Swift-XRT later reported no X-ray source at that position.
Wavelength coverage
- Gamma-ray: Fermi/GBM trigger and localization (GCN 43510).
- X-ray: Swift-XRT PC-mode follow-up at T0+64.9–86.3 ks; no source at the candidate position, with an upper limit (GCN 43527).
- Optical: GOTO detections with fading behavior (GCN 43514); NOT/ALFOSC non-detection with r > 22.75 from image subtraction at ~16.5 hr (GCN 43518).
No observations were mentioned in radio, infrared, ultraviolet, millimeter/sub-mm, or very-high-energy gamma rays.
Lightcurve and spectrum
- Optical: GOTO reports L=20.17±0.16 at +4.87 h fading to L=20.59±0.19 by +7.23 h; fade of 0.42±0.25 mag over 2.35 h, consistent with a power-law decay t^-0.92±0.38 (GCN 43514).
- X-ray: 3-sigma upper limit 0.003 ct s^-1, corresponding to 0.3–10 keV flux <1.0e-13 erg cm^-2 s^-1 (GCN 43527).
Redshift
What’s special vs typical
- The optical transient candidate is reported as coincident with a very nearby galaxy (PGC 139241) at a luminosity distance of ~53 Mpc and offset by ~9 arcsec from the nucleus, which would be unusually nearby for a GRB association (GCN 43514).
- Deep NOT imaging finds no obvious point source and sets a limit r>22.75 at ~16.5 hr, stated to be deeper than a simple extrapolation of the earlier optical decay (GCN 43518).
- Swift-XRT reports no X-ray source at the candidate position despite ToO follow-up (GCN 43527).