Fermi GBM Counterparts to LIGO Gravitational-Wave Candidates

As advanced LIGO begins operations, we eagerly anticipate the detection of gravitational waves (GW) in coincidence with a gamma-ray signal from the Fermi Gamma-ray Burst Monitor (GBM). The most likely source is a short Gamma-Ray Burst (GRB) arising from the merger of two neutron stars. With its broad sky coverage, GBM triggers and localizes more short GRBs than other active space missions, ~45 each year, with an estimate of <1-5 within the LIGO detection horizon. Combining GBM and LIGO localization uncertainty regions may provide a smaller region for GW host searches. A joint GBM-LIGO detection increases the confidence in the GW detection and helps characterize the parameters of the merger. Offline searches for weak GRBs that fail to trigger onboard Fermi indicate that additional short GRBs can be detected in the GBM data. I will discuss joint searches to detect and localize GW candidates, and explore how the non-detection in the GBM data of a signal consistent with GW candidates in the LIGO data can affect follow-up strategies for counterpart searches by other observers.