ISOLATED NEUTRON-STARS IN THE ROSAT SURVEY

Two very promising candidates for isolated old neutron stars (IONS) ac creting interstellar matter were found so far in ROSAT data. RXJ1856.5 -3754 and RXJ0720.4-3125 are soft X-ray sources with very similar X-ra y spectrum, long term temporal behaviour and faint optical counterpart . In addition RXJ0720.4-3125 shows 8.4 s pulsations which allow to con strain the magnetic field strength of the neutron star. We carried out a search for additional IONS with similar properties in the ROSAT all -sky survey data of the galactic plane and present RXJ0806.4-4123 as f urther promising candidate.