General information
GRB 260127B is a likely short GRB triggered by Fermi/GBM at 2026-01-27 20:02:32 UT with multiple independent high-energy detections and subsequent optical and X-ray follow-up.
Wavelength coverage
- Gamma-ray / hard X-ray: Detected by Fermi/GBM, Insight-HXMT/HE (60–900 keV), GECAM-B (~70–6000 keV), AstroSat/CZTI (20–200 keV; also veto 100–500 keV), and Konus-Wind (via IPN triangulation).
- X-ray: Swift-XRT ToO performed; no counterpart detected at the GOTO candidate position, with reported flux upper limits.
- Optical: GOTO reported a fading candidate (GOTO26aih/AT2026bnn) and MASTER-Net reported early upper limits.
No observations were mentioned in radio, infrared, ultraviolet, or TeV bands.
Lightcurve and spectrum
- Prompt duration: T90 = 0.17 (+0.04/-0.02) s (Insight-HXMT/HE) and T90 = 0.13 (+0.11/-0.02) s (GECAM-B); AstroSat/CZTI reports T90 = 0.17 (+0.11/-0.03) s; Fermi/GBM notes T90 of about 1 s (50–300 keV).
- Prompt morphology: Multi-pulses reported by Insight-HXMT/HE and GECAM-B; Fermi/GBM describes a single short peak.
- Prompt spectrum (Fermi/GBM, T0-0.1 to T0+0.3 s): cutoff power law with index -0.11 ± 0.01 and Epeak = 710 ± 30 keV; alternatively a Band model with Epeak = 570 ± 20 keV, alpha = -0.040 ± 0.002, beta = -2 ± 0.1.
- Prompt energetics (Fermi/GBM): fluence (10–1000 keV) (1.29 ± 0.09)E-06 erg/cm^2; 64-ms peak photon flux (10–1000 keV) 22 ± 2 ph/s/cm^2.
- Optical candidate photometry (GOTO26aih/AT2026bnn): L = 19.15 ± 0.14 AB mag at t0+5.66 h fading to L = 19.82 ± 0.11 at t0+7.91 h, with decay t^-1.66 ± 0.97; nondetection at t0-7.6 days to >20.8 AB mag.
- X-ray follow-up (Swift-XRT, 985 s PC mode at T0+70.4–71.4 ks): no detection consistent with the GOTO candidate; 3σ upper limit corresponds to 0.3–10 keV flux of 5.0e-13 to 6.9e-13 erg cm^-2 s^-1.
Redshift
GOTO reports that the candidate (GOTO26aih/AT2026bnn) is spatially coincident with SDSS J124952.79+664500.4, which has a spectroscopic redshift z = 0.12 (DESI Collaboration, 2025).
What’s special vs typical
A fading optical candidate with an associated host spectroscopic redshift (z=0.12) is reported for this short GRB, but the proposed candidate is explicitly stated to lie outside the IPN annulus and also lacks an XRT detection, making the association uncertain.