We discuss recent Chandra and XMM-Newton observations of the bright isolated neutron star RXJ1856.5-3754 and suggest that the absence of any line features is due to effects of a high magnetic field strength (~1013G). Using different models for the temperature distribution across the neutron star surface and assuming blackbody emission to fit the optical and X-ray spectrum, we derive a conservative lower limit of the "apparent`` neutron star radius of 16.5 km × (d/117 pc). This corresponds to the radius for the ''true`` (de-redshifted) radius of 14 km for a 1.4 Msolar neutron star, indicating a stiff equation of state at high densities. A comparison of the result with mass-radius diagrams shows that quark stars and neutron stars with quark matter cores can be ruled out with high confidence.
Nuclear Physics B Proceedings Supplements
- Pub Date:
- June 2004
- 6 page, 2 figures, "The Restless High-Energy Universe" Proceedings of the symposium dedicated to six years of successful BeppoSAX operations Amsterdam, May 5-8, 2003