  The discovery of gravitational wave (GW) events and the detection of
electromagnetic counterparts from GW170817 has started the era of
multimessenger GW astronomy.The field has been developing rapidly and in this
paper,we discuss the preparation for detecting these events with the ESA Gaia
satellite,during the 4th observing run of the LIGO-Virgo-KAGRA (LVK)
collaboration that has started on May 24,2023. Gaia is contributing to the
search for GW counterparts by a new transient detection pipeline called GaiaX.
In GaiaX, a new source appearing in the field of view of only one of the two
telescopes on-board Gaia is sufficient to send out an alert on the possible
detection of a new transient. Ahead of O4, an experiment was conducted over a
period of about two months. During the two weeks around New Moon in this period
of time, the MeerLICHT (ML) telescope located in South Africa tried (weather
permitting) to observe the same region of the sky as Gaia within 10 minutes.
Any GaiaX detected transient was published publicly. ML and Gaia have similar
limiting magnitudes for typical seeing conditions at ML. At the end of the
experiment, we had 11861 GaiaX candidate transients and 15806 ML candidate
transients, which we further analysed and the results of which are presented in
this paper. Finally, we discuss the possibility and capabilities of Gaia
contributing to the search for electromagnetic counterparts of gravitational
wave events during O4 through the GaiaX detection and alert procedure.
