  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.

High Energy Astrophysical Phenomena