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G. Pavlov, O. Kargaltsev (Pennsylvania State University), R. Romani (Stanford University), V. Zavlin (University of Strasbourgh)
We have recently detected four nearby pulsars, Vela, B0656+14, Geminga, and J0437-4715, with the STIS/FUV-MAMA detector aboard the Hubble Space Telescope and measured their far-UV spectra and pulsations in the 1,100--1,700 Å (7--11 eV) band. The middle-aged pulsars B0656+14 and Geminga show thermal (Rayleigh-Jeans) spectra, apparently emitted from the bulk of the neutron star (NS) surface. The high-energy (Wien) tails of these thermal spectra have been detected in soft X-rays, while the hard X-ray and optical-IR radiation of these pulsars is produced in their magnetospheres. The thermal far-UV radiation of B0656+14 and Geminga is pulsed, which can be explained by the effects of strong magnetic fields or/and absorption in the NS magnetosphere. The far-UV radiation of the young Vela pulsar is predominantly nonthermal. Its unusual pulse profile shows four peaks per period, similar to the optical pulsations and the X-ray pulsations above 2 keV. The far-UV radiation from the very old recycled PSR J0437-4715 is predominantly thermal, corresponding the NS surface temperature of about 0.1 MK, which means that a heating mechanism operates in millisecond pulsars. This temperature is too low to observe this radiation even in soft X-rays, where emission from hot polar caps dominates, while the optical emission is dominated by the white dwarf companion of the pulsar.
This work was supported by STScI grants GO-9098, GO-9182, and GO-9797, and NASA grant NAG5-10865.
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Bulletin of the American Astronomical Society, 36 #3
© 2004. The American Astronomical Soceity.