  Young isolated radio-quiet neutron stars are still hot enough to be
detectable at X-ray and optical wavelengths due to their thermal emission and
can hence probe cooling curves. An identification of their birth sites can
constrain their age. For that reason we try to identify the parent associations
for four of the so-called Magnificent Seven neutron stars for which proper
motion and distance estimates are available. We are tracing back in time each
neutron star and possible birth association centre to find close encounters.
The associated time of the encounter expresses the kinematic age of the neutron
star which can be compared to its characteristic spin-down age. Owing to
observational uncertainties in the input data, we use Monte-Carlo simulations
and evaluate the outcome of our calculations statistically. RX J1856.5-3754
most probably originated from the Upper Scorpius association about 0.3 Myr ago.
RX 0720.4-3125 was either born in the young local association TWA about 0.4 Myr
ago or in Tr 10 0.5 Myr in the past. Also RX J1605.3+3249 and RBS 1223 seem to
come from a nearby young association such as the Sco-Cen complex or the
extended Corona-Australis association. For RBS 1223 also a birth in Sct OB2 is
possible. We also give constraints on the observables as well as on the radial
velocity of the neutron star. Given the birth association, its age and the
flight time of the neutron star, we estimate the mass of the progenitor star.
Some of the potential supernovae were located very nearby (<100pc) and thus
should have contributed to the 10Be and 60Fe material found in the Earth's
crust. In addition we reinvestigate the previously suggested neutron star/
runaway pair PSR B1929+10/ zeta Ophiuchi and conclude that it is very likely
that both objects were ejected during the same supernova event.
