GRB 260127A

General information

GRB 260127A was detected in gamma-rays by Swift/BAT and Fermi/GBM (also reported by GECAM-B), with a well-localized Swift/XRT afterglow at RA=231.87939 deg, Dec=+6.76215 deg (90% radius 2.1 arcsec). An uncatalogued optical transient consistent with the XRT position was discovered and followed by multiple facilities.

Wavelength coverage

• Gamma-ray: Swift/BAT (trigger and refined analysis), Fermi/GBM (localization and spectral/fluence report), GECAM-B (70–6000 keV light curve and T90).
• X-ray: Swift/XRT enhanced position and refined spectral/light-curve analysis.
• UV/optical/NIR: Swift/UVOT (no credible afterglow candidate in initial products); optical detections/limits from LCO (r), MITSuME (g'/Rc/Ic), SVOM/C-GFT (i), NOT (r/i/z), COLIBRÍ (r, z-limit), SAO RAS/Zeiss-1000 (Rc), INASAN RC500 and Terskol K-800 (limits), MASTER-Net (clear-band limits).
• Radio:

Lightcurve and spectrum

• Prompt duration: Swift/BAT T90(15–350 keV) = 104.06 ± 19.41 s; Fermi/GBM T90(50–300 keV) ~ 36 s; GECAM-B T90(70–6000 keV) = 6 +1/-1 s.
• Prompt spectra: Swift/BAT time-averaged spectrum fit by power law with index 1.76 ± 0.15; fluence (15–150 keV) = (2.3 ± 0.2)×10^-6 erg/cm^2; 1-s peak photon flux (15–150 keV) = 2.1 ± 0.3 ph/cm^2/s. Fermi/GBM time-averaged spectrum fit by power law index −1.55 ± 0.04, or Comptonized with index −1.29 ± 0.06 and Epeak = 490 ± 25 keV; fluence (10–1000 keV) = (3.8 ± 0.2)×10^-6 erg/cm^2; 1-s peak photon flux (10–1000 keV) = 2.7 ± 0.5 ph/cm^2/s.
• X-ray: XRT WT photon index 2.14 (+0.20, −0.19) with excess absorption; PC photon index 1.75 ± 0.06 with total NH = 1.32 (+0.21, −0.20)×10^21 cm^-2 and excess significance 7.6σ. Optical photometry shows fading from Rc=19.4±0.2 at 1245 s and r=20.45±0.20 at ~27.3 min to r22.3 at ~12 hr and r=22.80±0.28 at 16–19.5 hr.

Redshift

What’s special vs typical