Soft X-ray and EUV Radiation from Polar Caps of the Millisecond Pulsar J0437--4715

We fitted the soft X-ray and EUV spectra and light curves observed from the nearby (d ~ 140 pc) binary millisecond pulsar J0437--4715 with model spectra and light curves of radiation emitted from hot pulsar polar caps. These models have been developed by us (Zavlin et al. 1996, A&A, submitted) for pure hydrogen, helium and iron polar cap atmospheres with low magnetic fields (B < 10(8-10(10)) G) with allowance for frequency-dependent anisotropy of the emergent radiation (limb-darkening) and the gravitational redshift and bending the photon trajectories. Our analysis of both the EUVE and ROSAT data indicates that the radiation may originate from two polar caps of areas =~ 2 - 3 km(2) covered with hydrogen and/or helium with an effective temperature of =~ (0.9-1.0)x 10(6) K; the positions of the caps coinciding with those inferred by Manchester & Johnston (1995, ApJ, 441, L65) from radio pulse polarization properties. We shall discuss implications of our results for models of radio pulsars. The work has been partly supported by NASA grant NAG5-2508 and INTAS grant 94-3834.