TITLE: GCN CIRCULAR NUMBER: 37558 SUBJECT: GRB 240918B: Fermi GBM Detection DATE: 24/09/19 15:47:35 GMT FROM: rachel.hamburg@ijclab.in2p3.fr The Fermi GBM team reports the detection of a likely LONG GRB. At approximately 20:56:58 UT on 18 Sep 2024, the Fermi Gamma-ray Burst Monitor (GBM) detected GRB 240918B, which was observed about 107 s after GBM triggered on GRB 240918A (trigger 748385716/240918872) (Fermi GBM Team 2024; GCN 37549). Due to the GBM trigger buffer of 10 min, the GBM did not trigger on this GRB. The on-ground calculated location, using the Fermi GBM trigger data from 107.52 s to 115.71 s after trigger time, is RA = 142.54, Dec = -17.36 (J2000 degrees, equivalent to J2000 9h 30m, -17d 36'), with a statistical uncertainty of 2.03 degrees. The angle from the Fermi LAT boresight is 64 degrees. The GBM Targeted Search [1], the most sensitive, coherent search for GRB-like signals, was also used to identify GRB-like emission around the time of GRB 240918B. This search finds a multi-peaked emission episode on timescales up to 4.096 s and showing a localization consistent with the on-ground location. The brightest peak (at 20:57:01 UT) was found to be the most significant (FAR = 5.4e-06 Hz) on the 0.512 s timescale and best fit with a "normal" GRB spectrum as described in [1]." [1] Goldstein et al. 2019 arXiv:1903.12597 View this GCN Circular online at https://gcn.nasa.gov/circulars/37558. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...