The X-ray emission properties of millisecond pulsars

Until now X-radiation from ten millisecond pulsars has been detected. In th e present paper we summarize the observations and show the results of a re- analysis of archival ROSAT data. In addition we present the results of rece nt observations of PSR J0437-4715 with the ROSAT PSPC and HRI detectors. We show that the pulsed fraction is independent of energy in the range 0.1-2. 4 keV. The pulse width as measured at X-ray energies is comparable with tha t observed in the radio domain. An upper limit for the X-ray luminosity of the pulsar's bow-shock visible in H-alpha is found to be L-x < 2 x 10(29) e rg s(-1) (d/180pc)(2). We further report on the discoveries of PSR J1024-07 19, J1744-1134 and J2124-3358 with the ROSAT-HRI, making them the first sol itary galactic millisecond pulsars detected at X-ray energies. The pulse pr ofile of PSR J2124-3358 shows marginal evidence for a double peak structure . We finally discuss the observed emission properties of the detected milli second pulsars and conclude that the measured power-law spectra and pulse p rofiles together with the close correlation between the pulsar's spin-down energy (E) over dot and the observed X-ray luminosity suggests a non-therma l origin for the bulk of the observed X-rays.