Frank Haberl: X-ray observations of Isolated Neutron Stars

The author presented a global view of X-ray observations of neutrons stars and the possible information that one can deduce from them. Evidence of multicomponent Xray spectra and pulsation of the Xray flux are evidence for a non-uniform temperature on the surface of the neutron star. Three middle aged pulsars (The three musketeers) present two thermal components (from the surface and a hot spot) and a power-law component (most probably coming from the magnetosphere). Pulse phase spectroscopy from Chandra and XMM showed that the hot and the cold blackbody components are not in phase.

XMM observations of the 7 known isolated neutron stars showed that they do not have pure blackbody spectra, indicating absorption features (even multiple lines). Several origins for those lines were mentioned, e.g. Cyclotron resonance, atomic lines transitions (Hydrogen). Those isolated neutron stars also provide a unique ways of measuring their magnetic fields using 2 independent method (magnetic dipole breaking and proton cyclotron absorption). Observations of RX J0720.4-3125 put forward the evidence for precession of the neutron star and the evidence of 2 polar caps.

Finally, the author showed with cooling curves analysis the evidence of magnetic field decay. The main conclusion from this presentation is that a NS model with a uniform temperature and a dipolar magnetic field is far too simple.