Detection of pulsed X-rays from the binary millisecond pulsar J0437 - 4715
Abstract
THE X-ray properties of pulsars (highly magnetized rotating neutron stars) depend mainly on the age of the star1. For young (<= 104 yr) pulsars, virtually all of the X-ray emission is pulsed, appearing as sharp bursts with a power-law spectrum; these emissions are thought to arise from the acceleration of electrons and positrons in the pulsar's magnetosphere2-5. Older pulsars, on the other hand, exhibit broad X-ray pulses, a lower pulsed fraction and black-body spectra; this is ascribed to thermal emission from the surface of the cooling neutron star, the modulation of the X-rays reflecting temperature inhomogeneities induced by the strong magnetic fields6,7. No thermal emission is expected for neutron stars older than ~106 yr (refs 8-10) in the absence of surface heating processes11-15. Here we report the discovery of pulsed X-ray emission from a ~2 × 109-yr-old neutron star: the binary milli-second pulsar J0437 - 4715. The spectral properties of the pulsed emission suggest a thermal origin, requiring substantial heating of the neutron-star surface either by internal friction11-13 or by energetic particles streaming onto the polar cap from the pulsar's magnetosphere14,15.
- Publication:
-
Nature
- Pub Date:
- October 1993
- DOI:
- 10.1038/365528a0
- Bibcode:
- 1993Natur.365..528B