2025RAA....25d4012L

We simulate the optical search for the gravitational-wave electromagnetic counterpart of a binary neutron star merger event (i.e., a kilonova) using the ground based SiTian project prototype telescope with a 5 minute limiting magnitude of 22.0, triggered by the LIGO and Virgo gravitational wave detectors during the ongoing O4 run. Our simulations show that an average of 0.17-0.25 kilonova events can be observed over the entire O4 period of ∼2 yr in the most optimistic case we set, while no kilonova can be detected in other cases. We note that it is beneficial for SiTian's kilonova searching to extend the exposure time to gain deeper limiting magnitude despite the rapid decline of kilonova luminosity.