TITLE: GCN CIRCULAR NUMBER: 38962 SUBJECT: GRB 250116A: Fermi GBM Observation of an Extremely Interesting Burst DATE: 25/01/16 20:44:37 GMT FROM: Ava Myers at NASA GSFC <ava.myers@nasa.gov> E. Bissaldi (Politecnico and INFN Bari), A. Myers (NPP/GSFC), O.J. Roberts (USRA), and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 12:33:59.53 UT on 16 January 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250116A (trigger 758723644/250116524). The angle from the Fermi LAT boresight is 55 degrees. The GBM light curve consists of multiple peaks, with an apparent duration (T90) of 15.9 s (50-300 keV). However, there is low energy emission that extends longer than the T90 out to at least several hundred seconds after the trigger time. The Sun emerges from Earth occultation midway during this burst, and thus due to the spacecraft motion during this time and the localization being relative close to the Sun position, it is currently unknown whether this is part of a long duration C-class Solar Flare or afterglow emission from the Burst. Analysis is ongoing. The time-averaged spectrum from T0+0 to T0+21 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.71 +/- 0.01 and the cutoff energy, parameterized as Epeak, is 462 +/- 6 keV. from T0+0 to T0+21 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.71 +/- 0.01 and the cutoff energy, parameterized as Epeak, is 462 +/- 6 keV. The event fluence (10-1000 keV) in this time interval is (9.97 +/- 0.05)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+17 s in the 10-1000 keV band is 43.9 +/- 0.4 ph/s/cm^2. Multi-wavelength follow up of this Burst is strongly encouraged. 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/38962. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...