  The recent discoveries of gravitational wave events and in one case also its
electromagnetic (EM) counterpart allow us to study the Universe in a novel way.
The increased sensitivity of the LIGO and Virgo detectors has opened the
possibility for regular detections of EM transient events from mergers of
stellar remnants. Gravitational wave sources are expected to have sky
localisation up to a few hundred square degrees, thus Gaia as an all-sky
multi-epoch photometric survey has the potential to be a good tool to search
for the EM counterparts. In this paper we study the possibility of detecting EM
counterparts to gravitational wave sources using the Gaia Science Alerts
system. We develop an extension to current used algorithms to find transients
and test its capabilities in discovering candidate transients on a sample of
events from the observation periods O1 and O2 of LIGO and Virgo. For the
gravitational wave events from the current run O3 we expect that about 16 (25)
per cent should fall in sky regions observed by Gaia 7 (10) days after
gravitational wave. The new algorithm will provide about 10 candidates per day
from the whole sky.
