The Importance of Fermi GBM in the Era of Gravitational-Wave Astronomy

The Fermi Gamma-ray Burst Monitor (GBM), with observing duty cycle of ~85%, surveys the entire sky that is not occulted by the Earth from 8 keV - 40 MeV with 2 microsecond temporal resolution and data downlinks of each individual photon count. Due to these characteristics, Fermi GBM is currently the most prolific detector of the prompt emission of short-duration gamma-ray bursts (GRBs), some of which are produced by binary neutron star mergers, as confirmed by the realtime simultaneous triggers of GBM and LIGO of GW170817/GRB 170817. The wealth of near-realtime data by the 14 independent detectors on GBM, with fine time and spectral resolution and the ability to localize signals, has enabled GBM to perform powerful sub-threshold searches for weak signals coincident with sub-threshold gravitational-wave signals. I will detail the results from these sub-threshold searches during LIGO's first observing run (O1), including the detection of the weak transient GW150914-GBM, discuss the detection of GW170817 and improvements to the sub-threshold searches during O2, and describe the plans and contributions by GBM to GW astrophysics during O3. I will also present results of archival searches of GBM data to estimate the detection rate of events with similar characteristics to GRB 170817A.