Constraining the geometry of the neutron star RX J1856.5−3754

摘要: RX J1856.5-3754 is one of the brightest, nearby isolated neutron stars (NSs), and considerable observational resources have been devoted to its study. In previous work, we found that our latest models a magnetic, hydrogen atmosphere match well entire spectrum, from X-rays optical (with best-fitting NS radius R ≈ 14 km, gravitational redshift Żg ∼ 0.2, magnetic field B 4 x 10 12 G). A remaining puzzle non-detection rotational modulation X-ray emission, despite extensive searches. The situation changed recently with XMM-Newton observations uncovered 7-s pulsations at ≈1 per cent level. By comparing predictions model (which includes simple dipolar-like surface distributions temperature) observed brightness variations, are able constrain geometry J1856.5-3754, angle <6° other ≈20°-5°, though solutions not definitive, given uncertainties. These angles indicate close alignment between rotation axes or axis observer. We discuss results in context being normal radio pulsar candidate for observation by future polarization missions such as Constellation-X XEUS.