TITLE: GCN CIRCULAR NUMBER: 43546 SUBJECT: GRB 260127A: Fermi GBM Observation DATE: 26/01/28 18:26:39 GMT FROM: atrigg2@lsu.edu A. C. Trigg (NPP ORAU, NASA MSFC) reports on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 17:51:07.74 UT on 27 January 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260127A (trigger 791229072/260127744), which was also detected by Swift BAT and XRT (N. J. Klingler et al. 2026, GCN 43529). The Fermi GBM real-time localization (GCN 43528) is consistent with the Swift BAT position. The angle from the Fermi LAT boresight is 88 degrees. The GBM light curve single emission episode with a duration (T90) of about 36 s (50-300 keV). The time-averaged spectrum from T0-15 to T0+32 s is best fit by a power law function. The power law index is -1.55 +/- 0.04. A Comptonized model fits the spectra equally well with power law index is -1.29 +/- 0.06 and the cutoff energy, parameterized as Epeak, is 490 +/- 25 keV. The event fluence (10-1000 keV) in this time interval is (3.8 +/- 0.2)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0-0.32 s in the 10-1000 keV band is 2.7 +/- 0.5 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/" View this GCN Circular online at https://gcn.nasa.gov/circulars/43546. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...