Updates to the Fermi GBM Targeted Sub-threshold Search in Preparation for the Third Observing Run of LIGO/Virgo

Understand

In this document, we detail the improvements made to the Fermi GBM targeted sub-threshold search for counterparts to LIGO/Virgo gravitational-wave triggers.

• We describe the implemented changes and compare the sensitivity of the O3 search to that of the version of the search that operated during O2.
• Overall, we have improved both the sensitivity and speed of the targeted search.
• Further improvements to the search have been made for the O3b observing run, including automated upperlimits estimation and incorporating the updated localization systematic with the new version of the search.