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J. Edelstein (1), R. S. Foster (2), and S. Bowyer (1)
1) Center for Extreme Ultraviolet Astrophysics, 2150 Kittredge
St., University of California, Berkeley, CA 94720--5030
2) Remote
Sensing Division, Code 7210, Naval Research Laboratory, Washington, DC
20 375
We report the first detection of extreme ultraviolet (EUV) emission from a millisecond pulsar. The EUV flux is not consistent with standard models used to describe the X-ray flux from this object. The size of an EUV-emitting hot polar cap disagrees with the size derived from the X-ray data by a factor from ~3 to 25. However, a blackbody with a temperature of ~5.7E+05 K and an area of ~3 km^2 can explain both EUV and X-ray observations below 0.4 keV. Alternatively, if the EUV emission is independent of the X-ray emission and is due entirely to a thermalized neutron star surface, we place a limit on the surface temperature of 1.6 - 4.0E+05$ K. Surface reheating would be required to explain this temperature according to standard neutron star cooling models because of the pulsar's 5 Gyr age. The EUV data rule out reheating by crust-core friction, accretion from the interstellar medium, accretion from the white dwarf companion, and heating by a particle-wind generated nebula. We use models of pulsar reheating by magnetic monopole catalysis of nucleon decay to establish an upper limit to the flux of monopoles in the Galaxy from 1 to 3 orders of magnitude below existing limits.
Keywords: pulsars: individual: PSR~J0437-4715---extreme ultraviolet: stars
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