  Gravitational waves (GW) can be emitted from coalescing neutron star (NS) and
black hole-neutron star (BH-NS) binaries, which are thought to be the sources
of short hard gamma ray bursts (SHBs). The gamma ray fireballs seem to be
beamed into a small solid angle and therefore only a fraction of detectable GW
events is expected to be observationally coincident with SHBs. Similarly
ultrahigh energy (UHE) neutrino signals associated with gamma ray bursts (GRBs)
could fail to be corroborated by prompt gamma-ray emission if the latter is
beamed in a narrower cone than the neutrinos. Alternative ways to corroborate
non-electromagnetic signals from coalescing neutron stars are therefore all the
more desirable. It is noted here that the extended X-ray tails (XRT) of SHBs
are similar to X-ray flashes (XRFs), and that both can be attributed to an
off-axis line of sight and thus span a larger solid angle than the hard
emission. It is proposed that a higher fraction of detectable GW events may be
coincident with XRF/XRT than with hard gamma-rays, thereby enhancing the
possibility to detect it as a GW or neutrino source. Scattered gamma-rays,
which may subtend a much larger solid angle that the primary gamma ray jet, are
also candidates for corroborating non-electromagnetic signals.
