Optical Properties and origin of Radio-Quiet X-ray Dim Isolated Neutron Stars

Christian Motch

Observatoire de Strasbourg


ROSAT has discovered a small group of X-ray emitting isolated neutron stars (INS) characterised by a lack of radio emission and a soft thermal-like X-ray spectrum. Weak interstellar absorption indicates relatively small distances of a few hundred parsecs and the absence of nearby SNR suggests middle-age objects or old neutron stars re-heated by accretion from the interstellar medium. Their proximity and the absence of strong non-thermal activity make them unique laboratories for testing radiative properties of neutron star surfaces, high gravity and high magnetic field physics. Most of these INS have optical counterparts from which contraints on the surface emitting properties can be derived. Optical imaging also allows sensitive searches for proper motion which can provide information on space velocity and birth place. I will report on the current problems faced by the modelling of the optical to X-ray energy distributions and will discuss the evolutionary status, age and origin of this particular population.


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