  Although the true origin of the broad absorption lines in X-ray spectra of
thermal isolated neutron stars is not clear yet, our current knowledge about
the "magnificent seven" strongly suggests that they are highly magnetized
($10^{13} - 10^{14}$ G), slowly rotating cooling neutron stars. Further timing
studies would be very useful to obtain more independent estimates of the
magnetic field strength (as they currently only exist from RX J0720.4-3125).
