  The detection of astrophysical neutrinos from transient sources can help to
understand the origin of the neutrino diffuse flux and to constrain the
underlying production mechanisms. In particular, proton-neutron collisions may
produce GeV neutrinos. However, at these energies, neutrino data from large
water Cherenkov telescopes, like KM3NeT and IceCube, are dominated by the
well-known atmospheric neutrino flux. It is then necessary to identify a
sub-dominant component due to an astrophysical emission based on time
correlation across messengers. The contribution covers several methods to
search for such a signal in short time windows centered on observed transient
sources, including a novel approach based on the distribution of time
differences. Their performance is compared in the context of subpopulations of
astrophysical sources that may show prompt or delayed neutrino emissions. The
outlook for the usage of such techniques in actual analyses is also presented.
