TITLE: GCN CIRCULAR NUMBER: 29536 SUBJECT: Fermi GBM Sub-Threshold Detection of GRB 210217A DATE: 21/02/18 22:22:40 GMT FROM: Joshua Wood at MSFC/Fermi-GBM C. Fletcher (USRA) reports on behalf of the Fermi-GBM Team: Swift-BAT detected GRB 210217A at 23:25:42 UT (GCN 29521). There was no Fermi-GBM onboard trigger around the event. An automated, blind search for short gamma-ray bursts below the onboard triggering threshold in Fermi-GBM identified a high reliability transient consistent in both time and location with the Swift BAT event. Link: https://gcn.gsfc.nasa.gov/notices_gbm_sub/635297147.fermi The GBM targeted search [1], the most sensitive, coherent search for GRB-like signals also identified a transient most significantly on the 1.024 s timescale, with a log likelihood ratio of 72 and a location consistent with the Swift BAT event. The GBM targeted search event was found with the highest significance with a "normal" spectrum (Band function with Epeak = 230 keV, alpha = -1.0, beta = -2.3) for a GRB. [1] Goldstein et al. 2019 arXiv:1903.12597