TITLE: GCN CIRCULAR NUMBER: 19096 SUBJECT: GRB 160225B: Fermi GBM detection DATE: 16/02/26 23:54:49 GMT FROM: C. Michelle Hui at MSFC/Fermi-GBM C. M. Hui (NASA/MSFC), E. Burns (UAH), and C. Meegan (UAH) reports on behalf of the Fermi GBM Team: At 19:24:25.39 UT on 25 February 2016, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 160225B (trigger 478121069 / 160225809) which was also triangulated by IPN (Svinkin et al., GCN 19095) The on-ground calculated location, using the GBM trigger data, is RA = 150.19 , DEC = -34.71 (J2000 degrees, equivalent to 10h 00m, -34d 42.0'), with an uncertainty of 1.00 degrees (radius, 1-sigma containment, statistical only; there is additionally a systematic error which we have characterized as a core-plus-tail model, with 90% of GRBs having a 3.7 deg error and a small tail suffering a larger than 10 deg systematic error. [Connaughton et al. 2015, ApJS, 216, 32]). The angle from the Fermi LAT boresight is 100 degrees. The GBM light curve shows two peaks with a duration (T90) of about 64 s (50-300 keV). The time-averaged spectrum from T0+43.009 s to T0+74.753 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.91 +/- 0.03 and the cutoff energy, parameterized as Epeak, is 124.10 +/- 3.30 keV. The event fluence (10-1000 keV) in this time interval is (1.434 +/- 0.023)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+54.27 s in the 10-1000 keV band is 12.89 +/- 0.37 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog.